To Make Streusel Topping: 

In a medium bowl, combine all dry ingredients until evenly mixed with a fork.  Pour in melted, cooled butter and toss to evenly combine.  Stir until no dry ingredients remain, and do not make into a paste.  You’ll want a combination of medium and large crumbles.  Put bowl into refrigerator until needed.

To Make Cream Cheese Filling:

Using a hand-held mixer, combine cream cheese and powdered sugar until smooth.  Set aside.

To Make Banana Nut Muffins:

Preheat oven to 350 degrees F.  Line a 12 cup muffin tin with muffin liners.  (I recommend using parchment paper tulip style liners to achieve a higher muffin.). Set aside.

In a large bowl, use a pastry cutter or a fork to cut the bananas into the granulated sugar.  (You’ll want to have smaller chunks of banana.). Stir in egg, oil, vanilla, cinnamon and nutmeg until well combined.  Add remaining dry ingredients and 3/4 c. walnuts.  Stir until no flour is visible.

Using an ice-cream scoop or a tablespoon, place about 1-2 T. of batter into the bottom of each muffin liner.  Scoop a tablespoon of cream cheese filling into the center of the batter.  Top each muffin with remaining batter.  Then top each muffin with streusel crumbles evenly using a tablespoon.  Sprinkle remaining 1/4-1/3 c. walnuts over each muffin.  Bake for 23-25 minutes or until a toothpick inserted in the center comes out clean.

Remove muffin tin to a wire rack for only 5 minutes.  After 5 minutes, remove individual muffins to the wire rack to cool completely.