Whole Wheat Banana Crumb Muffins

I've had this bookmarked and decided to whip these up. Smitten Kitchen made hers as Whole Wheat Apple Muffins, but I made ours as whole wheat banana crumb muffins. These were super moist day 2. They were gobbled up fast!

1 cup (4 ounces) whole wheat flour
1 cup (4 1/4 ounces) all-purpose flour
1 teaspoon baking powder
1 teaspoon baking soda
1/4 teaspoon salt
1 tablespoon cinnamon
1/2 cup (1 stick, 4 ounces) unsalted butter, at room temperature
1/2 cup (3 1/2 ounces) granulated sugar
1/4 cup light brown sugar, packed*
1 large egg, lightly beaten
1 cup (8 ounces) buttermilk
3-5 bananas, chopped* (depending how much banana you want)
crumb topping*

Preheat the oven to 450°F. Grease and flour an 18 cup muffin tin and set aside.
Mix together the flours, baking powder, baking soda, salt, and cinnamon, and set aside. In a separate bowl, cream the butter and add the granulated sugar and 1/4 cup of the brown sugar. Beat until fluffy. Add the egg and mix well; stop once to scrape the sides and bottom of the bowl. Mix in the buttermilk gently. (If you over-mix, the buttermilk will cause the mixture to curdle.) Stir in the dry ingredients and fold in the apple chunks (or bananas).

Divide the batter evenly among the prepared muffin cups, sprinkling the remaining 1/4 cup brown sugar on top (or crumb topping). Bake for 10 minutes, turn the heat down to 400°F, and bake for an additional 5 to 10 minutes, or until a toothpick inserted into the center of a muffin comes out clean. Cool the muffins for 5 minutes in the tin, then turn them out onto a wire rack to cool completely.

The crumb topping I found here

¼ cup pecans (ground)
½ cup all-purpose flour
½ cup packed brown sugar
pinch of salt
4 tablespoons butter, cold, cubed

In a food processor, grind ¼ cup of almonds. Add the flour, brown sugar and salt, and pulse until blended. Add the butter and pulse until the mixture resembles coarse crumbs. (you will have leftovers, just keep stored in the freezer for next use)