In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

In a large bowl or stand mixer, cream the softened butter and granulated sugar until light and fluffy.

Add the egg, sourdough discard, and vanilla extract. Mix until fully combined.

Gradually add the dry ingredients to the wet ingredients and mix until a smooth dough forms.

Place the dough between two sheets of parchment paper and roll to about 1/4-inch thickness.

Transfer the dough (still between parchment) to the refrigerator and chill for at least 30 minutes, or up to a couple of hours.

Tip: The dough can be made ahead and chilled overnight -- I've tried it and it works great!

Preheat the oven to 350°F.

Line a baking sheet with parchment paper and set aside.

Remove the dough from the refrigerator and use cookie cutters to cut out shapes.

Place cookies on the prepared baking sheet.

Bake for 10 minutes, or until the edges are just set and the tops remain pale.

Let cookies rest on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.

While the cookies cool, beat the softened butter until smooth and creamy.

Gradually add the powdered sugar, mixing well between additions.

Add vanilla extract and milk, one tablespoon at a time, until the frosting reaches your desired consistency.

Mix in food coloring if using. I used dragon fruit powder to get the pinkish hues.

Frost cooled cookies and finish with sprinkles if desired.