Steps
1. Preheat oven to 185°C.
2. Grease and flour a medium-sized baking tin.
3. In a bowl, combine the mashed banana, butter, egg, and milk. Beat until light and fluffy.
4. Fold in the oatmeal.
5. Pour the mixture into the prepared baking tin.
6. Bake in preheated oven for 25 minutes or until a toothpick inserted into the center of the cake comes out clean.
7. Let the cake cool before slicing and serving.