Mix in the sour cream, then eggs, one at a time, mixing in between.
1 cup (250g) sour cream, 2 large eggs
Mix in the mashed bananas and vanilla extract. Then slowly stir in the flour mixture until just combined. Spoon the batter into the prepared baking pan.
Spread on cake, and top with chopped walnuts, chocolate shavings or banana slices (just before serving) if desired.
Notes
Leftovers can be covered up and stored in the fridge for up to 5 days.To freeze - Tightly wrap in saran wrap, then in foil, label with date, and store in the freezer for up to 3 months.