Preheat oven to 375°F (190°C). Line 18 standard muffin cups with paper liners or coat the cups with a cooking spray with flour.
Using an electric mixer on medium speed, beat the cream cheese, sugar, vanilla, and egg yolk until thoroughly combined.
Refrigerate while you make the muffin batter.
To make the muffins:
Whisk together the flour, sugar, brown sugar, baking powder, baking soda, and salt. Make a well in the center of the mixture. Set aside.
In a separate bowl, combine the butter, milk, egg, and vanilla until thoroughly mixed. Add to the well in the flour mixture, and mix just until a few streaks of flour remain.
Stir in the bananas, mixing just until combined.
Fill each muffin cup with approximately 2 tablespoons (#30 scoop) of muffin batter. Add approximately 1/2 tablespoon (#110 scoop) of the cream cheese mixture in the center of the batter. Then add approximately 1 tablespoon (#50 scoop) of the remaining muffin batter on top of the cream cheese filling.
If you like, sprinkle the top of each muffin with 1/4 to 1/2 teaspoon of chopped pecans and a pinch of sanding sugar.
Bake 22 to 26 minutes, or until a pick inserted into the center comes out clean. Cool in the pans for 10 minutes before serving.