1. Preheat the oven to 350°F. Line 15 cups of two muffin tins with paper liners or coat with nonstick spray.
2. In a small bowl, whisk together the flour, baking powder, baking soda, and salt.
3. Using a hand mixer, combine the egg, oil, brown sugar, and vanilla. Mix on low speed until light and creamy, about 5 minutes. Add the flour mixture in three additions, alternating with the buttermilk, beginning and ending with the dry ingredients. Scrape down the sides and bottom of the bowl, mixing just until you no longer see streaks of flour. Fold in the fruit without breaking it up.
4. Evenly scoop the batter into the prepared muffin tins. Each cup should be about halfway full to make room for the crumb topping. Add a generous amount of crumb topping (about 1/4 cup) to each muffin, squeezing the crumb together and then pressing gently on the muffins so it doesn’t fall off.
5. Bake for 22 to 24 minutes, or until a cake tester inserted in the centers comes out clean.
6. Let the muffins cool in the pans for 5 to 10 minutes. Transfer to a rack to cool completely.

Makes: 15 muffins