Mash the bananas with lemon juice with a fork. Whisk the egg, cane sugar, butter or margarine and quark together. Mix the flour, baking powder and cocoa and fold into the egg-butter mixture. Mix briefly. Grease the muffin tin or line it with paper liners. Pour in the batter. Bake in a preheated oven at 160 ° C for about 20 minutes. Take out and let cool.
In the meantime, stir together the cream cheese, quark, Nutella and powdered sugar. Pour in enough cream to make a nice, homogeneous cream. Remove the muffins from the molds and cut off a lid. Fill the muffins with cream, put the lid on. Dust with icing sugar if necessary.
Tip:
If you like, make a little more cream and decorate the lid with it, add a slice of banana and some powdered sugar.