# Required ingredients:
→ Muffins
01 - 1 cup all-purpose flour
02 - 1 cup whole wheat flour
03 - 1 cup granulated sugar
04 - 1 teaspoon baking powder
05 - 1/2 teaspoon baking soda
06 - 1/2 teaspoon salt
07 - 2 large eggs
08 - 1/2 cup vegetable oil or melted butter
09 - 1 cup sourdough discard, unfed
10 - 1/2 cup whole milk
11 - 1 teaspoon vanilla extract
12 - Zest of 1 large lemon
13 - 2 tablespoons fresh lemon juice
14 - 1 1/2 cups fresh or frozen blueberries
→ Crumb Topping
15 - 1/2 cup all-purpose flour
16 - 1/3 cup light brown sugar
17 - 1/4 cup cold unsalted butter, cubed
18 - Pinch of salt
19 - Zest of 1/2 lemon
# How to make it:
01 - Preheat oven to 375°F. Line a 12-cup muffin tin with paper liners or grease thoroughly.
02 - In a medium bowl, whisk together all-purpose flour, whole wheat flour, sugar, baking powder, baking soda, and salt until evenly distributed.
03 - In a large bowl, whisk eggs, oil, sourdough discard, milk, vanilla extract, lemon zest, and lemon juice until thoroughly combined.
04 - Gradually fold dry ingredients into wet mixture using a spatula until just combined, avoiding overmixing.
05 - Gently fold blueberries into batter, preserving their integrity. If using frozen blueberries, do not thaw beforehand.
06 - Distribute batter evenly among muffin cups, filling each approximately 3/4 full.
07 - In a small bowl, combine flour, brown sugar, cold cubed butter, salt, and lemon zest. Use fingers or pastry cutter to blend until mixture resembles coarse breadcrumbs.
08 - Sprinkle crumb topping generously over each filled muffin cup.
09 - Bake for 22 to 25 minutes until a toothpick inserted into center emerges clean and tops are golden brown.
10 - Cool muffins in pan for 5 minutes, then transfer to wire rack for complete cooling.