Preheat oven to 350°. Lightly grease a muffin tin with non-stick cooking spray or vegetable oil, or line with paper muffin liners.
Prepare streusel topping and set aside.
In a small bowl, whisk together flour, baking powder, baking soda and salt; set aside.
Combine sugar, melted butter, sour cream, eggs and vanilla in a large mixing bowl; beat until well blended. Stir in bananas. Add flour mixture to banana mixture, stirring just until moistened. Mix in chocolate chips and nuts.
In a small bowl, whisk together sugar and flour. Add butter and mix until mixture has a sandy texture. Mix in almonds.
Divide batter evenly into 12 muffin cups. Sprinkle muffins with streusel topping.
Bake at for 20 to 25 minutes, until a tester inserted into the center comes out clean.
Cool muffins for five minutes in the muffin pan before removing to a wire rack to cool.