Sourdough Discard Custard-Filled Donuts
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These sourdough discard donuts are filled with a homemade vanilla custard. They are soft, fluffy, and are *so* much better than bakery donuts (homemade donuts always are!).
I recently shared my brioche sourdough glazed donut recipe and heard from so many of you how much you enjoyed them! So if you loved those ones, you’re going to adore these vanilla custard-filled bombolini-inspired donuts!
This recipe calls for active dry yeast and sourdough discard (inactive sourdough starter); however, you can certainly use active, bubbly sourdough starter.
And this vanilla custard recipe goes back generations. My great-grandmother used to make a vanilla custard very similar to this one (I used her recipe to branch off of). So it holds a special place in my heart.
Looking for more sourdough recipes? Check these out:
- sourdough strawberry white chocolate bread
- sourdough sugar cookies
- sourdough white chocolate raspberry cookies
Ingredients
For the Vanilla Custard
- Egg yolks
- Cornstarch
- Whole milk
- Granulated sugar
- Salt
- Vanilla extract – Vanilla bean paste also works great (it’s what I use and it provides such depth of flavor, plus those little specks in the custard!)
For the Sourdough Donut Dough
- Warm milk – around 105-110 degrees Fahrenheit
- Active dry yeast
- Granulated sugar
- Large egg
- Salt
- Sourdough discard (unfed) – you can use active, bubbly sourdough starter as well, but the yeast is what we use to get the rise.
- All-purpose flour
- Salted butter, room temperature
For Frying & Coating
- Neutral oil (for frying) – I have used coconut oil and vegetable oil. Avocado oil is another fantastic choice!
- Granulated sugar (for coating)
Step-by-Step Instructions
You’ll want the custard fully chilled before filling the donuts, so start here.
In a medium bowl, whisk together:
- 5 egg yolks
- 1/4 cup (30 g) cornstarch
Whisk until completely smooth and set aside.
In a saucepan over medium heat, combine:
- 2 cups (480 g) milk
- 1/2 cup (100 g) granulated sugar
- 1/4 teaspoon salt
Whisk occasionally and heat until the mixture is steaming but not boiling.
Now temper the eggs: slowly drizzle about 1 cup of the hot milk mixture into the egg mixture while whisking constantly. This prevents the eggs from scrambling.
Pour the tempered egg mixture back into the saucepan, whisking continuously. Cook over medium heat for 3–5 minutes, whisking constantly, until thick and creamy.
Remove from heat and stir in:
- 1 teaspoon vanilla extract
Transfer the custard to a bowl and press plastic wrap directly onto the surface to prevent a skin from forming. Refrigerate until completely chilled.
In a small bowl, combine:
- 2/3 cup (150 g) warm milk (105–110°F)
- 2 1/4 teaspoons (7 g) active dry yeast
- 1/4 cup (50 g) granulated sugar
Let sit for 5–10 minutes until foamy and bubbly.
In the bowl of a stand mixer fitted with a dough hook, add:
- Activated yeast mixture
- 1 large egg
- 1 teaspoon (6 g) salt
- 3/4 cup (200 g) sourdough discard
- 3 1/2 cups (425 g) all-purpose flour
Mix on medium speed until combined.
With the mixer running, add:
- 5 tablespoons (75 g) room temperature salted butter
Add the butter one tablespoon at a time, allowing it to fully incorporate before adding more.
Continue kneading on medium-high speed for 8–10 minutes, until the dough is soft, smooth, and pulling away from the sides of the bowl.
Transfer the dough to a lightly oiled bowl. Cover and let rise in a warm spot for about 2 hours, or until doubled in size.
You’re looking for a puffy, airy dough that springs back slowly when gently pressed and has about doubled in size as shown.
Punch down the dough and roll it out on a lightly floured surface to about 1/2-inch thickness.
Use a round cookie cutter (or the rim of a glass) to cut circles. Re-roll out the dough until you have used it all.
Place each donut onto an individual square of parchment paper. This makes transferring to hot oil much easier later.
Cover the shaped donuts lightly and let rise again for 1–2 hours, until visibly puffy and almost doubled in size.
They should look light and airy (as shown above) before frying.
Heat 2–3 inches of neutral oil in a heavy-bottomed pot to 340–360°F.
Carefully lower the donuts into the oil (you can use the parchment squares to help guide them in, then remove the paper with tongs).
Fry for 1–2 minutes per side, until golden brown.
Transfer to a wire rack with parchment underneath to catch drips.
While still warm, roll each donut in:
- 1 1/2 cups (300 g) granulated sugar
Return to the rack to cool completely before filling.
Transfer the chilled custard to a piping bag fitted with a round tip.
Use a butter knife to gently create a small hole in the side of each donut.
Pipe custard into the center until filled.
You’ll feel the donut slightly expand as it fills.
Equipment Needed
You don’t need anything fancy, but having the right tools will make these sourdough discard custard-filled donuts much easier and more consistent.
- Stand mixer with dough hook attachment
Makes kneading the enriched dough much easier. (You can knead by hand, but it will take longer.) - Mixing bowls
One medium bowl for the custard and one large bowl for rising the dough. - Medium saucepan
For cooking the custard. - Whisk
Essential for smooth, lump-free custard. - Rubber spatula
Helpful for scraping down bowls and stirring custard. - Plastic wrap
To press directly onto the custard and prevent a skin from forming. - Rolling pin
For rolling out the donut dough evenly. - Round cookie cutter or drinking glass (about 2½–3 inches)
For cutting uniform donut rounds. - Parchment paper (cut into small squares)
Makes transferring donuts into hot oil much easier and safer. - Heavy-bottomed pot or Dutch oven
Helps maintain steady oil temperature while frying. - Clip-on thermometer or instant-read thermometer
Critical for keeping oil between 340–360°F for perfectly cooked donuts. - Slotted spoon or spider strainer
For safely removing donuts from hot oil. - Wire cooling rack
Allows excess oil to drain and prevents soggy bottoms. - Piping bag with round tip
For filling donuts neatly with custard. - Small paring knife or butter knife
To create a hole for piping the custard.
Helpful Tips for Perfect Sourdough Donuts
- Temper the eggs verrrry slowly when making custard to prevent scrambling.
- If your custard becomes lumpy, strain it through a fine mesh sieve immediately.
- Custard thickens as it chills — remove it from heat once thickened to avoid overcooking.
- If yeast does not foam, your milk may have been too hot or too cold or the yeast has expired. Start again for best results.
- The dough should pass the windowpane test — stretch a small piece thin enough to see light through it.
- Avoid adding too much extra flour. Enriched dough should be soft and slightly tacky.
- Room temperature butter incorporates more smoothly than cold butter.
- Do not twist your cutter when shaping donuts — press straight down to allow proper rising.
- Underproofed donuts will be dense. Properly proofed donuts look airy and spring back slowly when pressed.
- Use a thermometer when frying.
- Too hot = dark outside, raw inside.
- Too cool = greasy donuts.
- Fry in small batches to maintain oil temperature (I fry 2-3 at a time).
- Fill donuts just before serving for the freshest texture.
Serving & Storage
These are best enjoyed the same day for maximum softness.
Store leftovers in an airtight container in the refrigerator for up to 3 days. Bring to room temperature before serving.
Sourdough Discard Custard-Filled Donuts
Ingredients
Vanilla Custard (Make Ahead)
- 5 large egg yolks
- 1/4 cup cornstarch 30 g
- 2 cups whole milk 480 g
- 1/2 cup granulated sugar 100 g
- 1/4 teaspoon salt 1.5 g
- 1 teaspoon vanilla extract or vanilla bean paste (I used the paste which is why you see speckles in the custard) 5 g
Donut Dough
- 2/3 cup warm milk 150 g, about 105–110°F
- 2 1/4 teaspoons active dry yeast 7 g
- 1/4 cup granulated sugar 50 g
- 1 large egg 50 g, room temperature
- 1 teaspoon salt 6 g
- 3/4 cup sourdough discard unfed (200 g)
- 3 1/2 cups all-purpose flour 425 g
- 5 tablespoons salted butter room temperature (75 g)
For Frying & Coating
- Neutral oil for frying about 2–3 inches deep; coconut, avocado, or vegetable oil
- 1 1/2 cups granulated sugar 300 g for coating
Instructions
Step 1: Make the Custard (Prepare Ahead)
- In a medium mixing bowl, whisk together the egg yolks and cornstarch until completely smooth. Set aside.
- In a medium saucepan over medium heat, combine the milk, sugar, and salt. Whisk and heat until the mixture is steaming but not boiling.
- Scoop out about 1 cup (240 g) of the hot milk mixture and slowly drizzle it into the egg mixture while whisking constantly. This tempers the eggs and prevents scrambling.
- Gradually pour the tempered egg mixture back into the saucepan with the remaining milk, whisking continuously.
- Cook over medium heat, whisking constantly, for 3–5 minutes or until thickened.
- Remove from heat and stir in the vanilla extract.
- Transfer custard to a clean bowl. Press plastic wrap directly onto the surface to prevent a skin from forming. Refrigerate until completely chilled (at least 2 hours).
Step 2: Make the Donut Dough
- In a small bowl, combine the warm milk, yeast, and sugar. Let sit for 5–10 minutes until foamy.
- In the bowl of a stand mixer fitted with a dough hook, add the yeast mixture, egg, salt, sourdough discard, and flour.
- Mix on medium speed until combined, scraping down the bowl as needed.
- With the mixer running, add the softened butter one tablespoon at a time, allowing each addition to incorporate before adding more.
- Knead on medium-high speed for 8–10 minutes, until the dough is soft, smooth, and pulling away from the sides of the bowl.
Step 3: First Rise
- Transfer the dough to a lightly oiled bowl.
- Cover and let rise in a warm place for about 2 hours, or until doubled in size.
Step 4: Shape & Second Rise
- Punch down the dough and roll it out on a lightly floured surface to about 1/2-inch thickness.
- Cut into rounds using a cookie cutter or the rim of a glass. Re-roll excess dough and cut into more round shapes until you've used it all.
- Place each donut onto an individual square of parchment paper on a baking sheet.
- Cover lightly with plastic wrap or a light towel and let rise again for 1–2 hours, until puffy and nearly doubled.
Step 5: Fry the Donuts
- Heat 2–3 inches of neutral oil in a heavy-bottomed pot to 340–360°F.
- Carefully lower donuts into the hot oil (working in batches).
- Fry 1–2 minutes per side, until golden brown.
- Transfer to a wire rack with parchment underneath.
- While still warm, roll each donut in granulated sugar. Return to rack to cool.
Step 6: Fill the Donuts
- Transfer chilled custard to a piping bag fitted with a round tip.
- Once donuts are fully cooled, use a butter knife to create a small hole in the side or center.
- Pipe custard into each donut until filled.
These donuts are truly so good! If you love filled donuts, these sourdough discard ones are a fantastic way to use up leftover sourdough discard!