Preheat oven to 350°F (180°C) and grease a 12-cup muffin tin or line with paper liners.
In a bowl, combine flour, sugar, baking powder, and salt.
Add melted butter, vanilla extract, and egg to the dry ingredients; stir until just combined.
Spoon 1 to 2 tablespoons of batter into each muffin cup and bake for 8 to 10 minutes until lightly golden.
Remove the base from oven and allow to cool completely.
In a separate bowl, beat cream cheese, mashed bananas, powdered sugar, and vanilla extract until smooth.
Gently fold whipped heavy cream into the banana cream mixture until combined.
Fill each cooled muffin cup with the banana cream filling using a spoon or piping bag.
Chill assembled cups in the refrigerator for at least 1 hour to set.
Before serving, top with optional whipped cream, banana slices, and chocolate shavings or sprinkles.