Combine the flour, brown sugar, and salt in a medium bowl. Add the butter and rub it between your fingers until the mixture resembles a coarse meal. Stir in the granola clusters and mix to combine.
Preheat the oven to 350°F. Grease a 12-cup muffin pan or line each cavity with muffin liners.
In the bowl of an electric mixer fitted with the paddle attachment, cream the butter, sugar, and brown sugar to combine.
Add the eggs one at a time, mixing to incorporate and scraping well after each addition. Add the vanilla and mix to combine.
Remove the bowl from the mixer, and fold in the mashed bananas. Add the flour, baking soda, and salt and mix just until incorporated.
Scoop the batter evenly into the prepared baking pan. Top each muffin with a few tablespoons of streusel (I like a lot). Bake until a tester inserted into the center of the muffin comes out clean, 20-25 minutes. Cool in the pan for 10 minutes, then remove from the pan and continue cooling on a wire rack.
I always have three kinds of hot sauce in my purse. I have a soft spot for making people their favorite dessert, especially if it's wrapped in a pastry crust. My newest cookbook, The Book on Pie, is out on November 10th, 2020.