1. Preheat oven to 375°F (190°C) and line a 12-cup muffin pan with liners or grease the cups.

2. In a bowl whisk the flour, baking powder, baking soda, salt, cinnamon, ginger, and nutmeg until combined.

3. In a large bowl stir together pumpkin purée, sourdough discard, brown sugar, oil, eggs, and vanilla extract until smooth.

4. Add the dry ingredients to the wet ingredients in two additions, mixing gently until just combined.

5. In a small bowl combine flour, brown sugar, granulated sugar, cinnamon, and salt, then cut in cold butter until coarse crumbs form.

6. Divide batter among the muffin cups, filling each two-thirds full, and top each with streusel crumb, pressing lightly.

7. Bake for 18–22 minutes until tops are golden and a toothpick inserted in the center comes out with moist crumbs.

8. Cool muffins in the pan for five minutes then transfer to a wire rack to cool completely.