Grind oats finely in a blender to make oatmeal.
Mash the banana with a fork.
In a bowl, combine the mashed banana, oatmeal, eggs, milk, baking powder, and salt. Mix well.
Add nuts or chocolate chips if desired.
Pour the batter into a pan lined with parchment paper.
Bake at 180℃ (356℉) in a preheated oven for 35-40 minutes.
Cool and slice to serve.