Preheat the oven to 425°F (218°C).

Line a standard 12-cup muffin pan with paper liners. For tall, bakery-style muffins, fill every other muffin cup, leaving an empty cup between each muffin.

In a small bowl, combine the flour and brown sugar.

Add the grated, very cold butter and use a fork or your fingertips to work the butter into the dry ingredients until coarse crumbs form.

Place the crumble topping in the refrigerator while you prepare the muffin batter.

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

Set aside.

In a large mixing bowl, whisk together the melted butter and granulated sugar until well combined.

Add the eggs and whisk until smooth.

Whisk in the vanilla extract, Greek yogurt, and sourdough discard until fully incorporated.

Gradually add the dry ingredients to the wet ingredients, folding gently with a rubber spatula until just combined.

Place the blueberries in a small bowl and toss them with the remaining 2 tablespoons of flour.

Gently fold the coated blueberries into the batter until evenly distributed.

Divide the batter evenly between every other muffin cup, filling each liner nearly to the top.

Scatter a few additional blueberries over each muffin, then generously sprinkle the crumble topping over the batter, gently pressing it down so it adheres.

Bake at 425°F (218°C) for 10 minutes.

Without opening the oven door, reduce the oven temperature to 350°F (177°C) and continue baking for 12-15 minutes, or until the tops are golden brown and a toothpick inserted into the center comes out clean or with a few moist crumbs.

Allow the muffins to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.

Serve warm or at room temperature.