Preheat your oven to 425°F. Line a jumbo muffin pan or a standard muffin pan with liners.

In a medium bowl, combine the flour, baking powder, baking soda, salt, granulated sugar, and brown sugar.

In a separate bowl, whisk together the sourdough discard, eggs, milk, melted butter, and vanilla.

Add the wet ingredients to the dry ingredients and stir just until combined. Don't overmix.

Gently fold in the raspberries.

For the streusel, combine the flour, brown sugar, and cinnamon. Cut in the cold butter with a fork or pastry cutter until crumbly.

Divide the batter evenly among the muffin cups, filling them nearly to the top for those giant bakery-style muffins.

Sprinkle generously with streusel topping.

Bake at 425°F for 5 minutes, then reduce the temperature to 350°F without opening the oven door.

Continue baking for 18–22 minutes, or until the tops are golden and a toothpick inserted into the center comes out mostly clean.

Cool in the pan for 10 minutes before transferring to a wire rack.