Preheat oven to 350° F. Line 12 muffin tins with paper cups.
Use a food processor to grind gingersnap cookies into a fine crumb. Melt butter in a microwave-safe bowl until melted. Combine melted butter with cookie crumbs and stir until there are no dry crumbs left. Divide ginger snap crumbs between the 12 muffin cups. Press down with a spoon or tart shaper.
Cookie Cups
Cream together sugar and butter. Add egg and vanilla, mix again, then add the sour cream, salt and soda. Add flour and beat until smooth.
Divide batter evenly between muffin cups.
Bake for 20 minutes or until they test done with a wooden pick.
Allow cookies to stand for 1-2 minutes after taking them out of the oven. Spray the round side of a 1 tsp measuring spoon with non-stick spray. Press down into the center of each cookie to create a well. Let cool completely.
Banana Cream Mousse Filling
While the cookie cups are cooling, prepare the banana cream mousse filling. Whisk together the box of dry pudding mix and the milk. Add in the whipped topping and stir GENTLY until combined. Transfer to a pastry bag or a zip lock bag and store in the fridge until the cookies are fully cool.
Take cookie cups out of muffin tin. Pipe banana cream mousse into each cup and top with a slice of banana. Sprinkle with a small amount of gingersnap cookie crumbles.