Preheat oven to 325°F. Grease and flour an 8½x4½-inch loaf pan with cooking spray and set aside.

In a medium bowl, whisk together flour, salt, baking soda, and baking powder. In a separate bowl, whisk together mashed banana, sugar, eggs, oil, milk, and vanilla until well incorporated. Fold in the flour mixture just until combined.

In a small microwave-safe bowl, heat peanut butter on high for 15 seconds. Give it a stir and heat for another 10 to 15 seconds or until melted and pourable. Spoon half of batter into the prepared pan and then spoon half of warm peanut butter over batter. Top with remaining batter and remaining peanut butter. Using a butter knife or long wooden skewer, gently swirl the two together.

To make the crumb topping, in a medium bowl, whisk together the flour, sugar, cinnamon and salt. Add the butter and rub it in with your fingers until it resembles coarse crumbs. Stir in the peanuts, peanut butter chips and sprinkles.

Sprinkle the crumb topping over the batter and bake until a wooden pick inserted in the center comes out clean, about 1 hour and 25 minutes. Let cool in pan for 10 minutes before removing onto a wire rack to cool completely. Slice and serve. Leftovers can be wrapped in plastic or stored in an air tight container at room temperature for up to 3 days. Enjoy!