To prepare a banana oat muffins with sour cream recipe, first you need to prepare your ingredients. First, you'll need: 1 cup of brown sugar, 1 teaspoon of baking powder, 2 tablespoons of cinnamon, and 1 tablespoon of nutmeg. Then, add your wet ingredients to the dry ingredients and mix them together until they're just combined. Now, it's time to add the bananas. You can use any type of banana you like, but I like to use kiwi, banana, mango, pineapple, or any other banana that I can get my hands on. Once you have all of the ingredients mixed together, pour the batter into muffin tins and bake them in the oven for 20 to 25 minutes.