Preheat oven to 350°F and spray one 12-cup muffin pan with cooking spray or use paper or silicone liners.
In a bowl, mix oats, salt, baking powder and cinnamon.
In another large bowl, mix egg whites, vanilla, coconut oil, stevia and mashed bananas until combined. Dump dry ingredients into wet ingredients; mix well. Pour in almond milk and stir until combined.
Gently stir in walnuts and raisins.
Scoop mixture evenly into muffin cups.
Bake 30-35 minutes or until the center of each baked oatmeal cup is set and a toothpick comes out clean. Enjoy immediately or allow cups to cool and store them in the fridge for 5-7 days or in the freezer for up to 3 months.
Reheat them in the toaster oven or microwave when you're ready to eat. If frozen take them out of the freezer and put them in the fridge the night before to thaw. Toast or microwave for a few seconds before enjoying.