makes 12 muffins
For the muffins:
1/4 cup unsalted butter
1 cup buttermilk
1 large egg
2 teaspoons pure vanilla extract
1 1/4 cup unbleached all-purpose flour
1 cup whole wheat pastry flour
2/3 cup packed brown sugar
2 teaspoons baking powder
1/4 teaspoon fine sea salt
2 teaspoons ground cinnamon
1/4 teaspoon ground nutmeg
1/8 teaspoon ground ginger
dash of ground allspice
1 1/2 cups peeled, cored, and finely chopped (about 1/4" pieces) apple (I used Liberty apples, which are a slightly tart variety)
For the crumble topping:
1 tablespoon brown sugar
2 tablespoons granulated sugar
1/4 cup unbleached all-purpose flour
1/2 teaspoon cinnamon
1/4 teaspoon fine sea salt
2 tablespoons unsalted butter, cut into cubes, at room temperature
1. Preheat the oven to 400 degrees. Line a muffin tin with paper liners. I find that spraying the liners lightly with cooking spray ensures the liners peel off easily after the muffins have baked.
2. Melt the butter on the stovetop or in a microwave. Set aside to cool.
3. In a small bowl, whisk together the buttermilk, egg, and vanilla. In a separate bowl, whisk together the flours, brown sugar, baking powder, salt, cinnamon, nutmeg, ginger, and allspice. Pour the cooled melted butter into the flour mixture and stir to combine.
4. Add the buttermilk mixture to the flour mixture. Stir to combine, but do not overmix. Fold in the apples. Divide the batter (it will be thick) evenly into the prepared muffin cups. (Each muffin cup should be filled to the top.)
5. In a small bowl, stir together the sugars, flour, cinnamon, and sea salt with a fork. Use the fork or a pastry blender to incorporate the butter into the sugar mixture, forming pea-sized crumbles. Sprinkle the crumble mixture evenly over top the muffins.
6. Bake the muffins in the oven for 18-20 minutes, or until the muffins are lightly browned and a toothpick inserted into the center of a muffin comes out clean. Remove the muffins from the oven and let cool in the tin for 5 minutes. Then remove the muffins from the tin and let cool completely on a wire rack. Any remaining muffins can be stored in an airtight container at room temperature for 2-3 days, though they are best eaten the day they are baked.