Preheat your oven to 350°F (175°C) to ensure even baking.
Lightly grease a muffin tin or line it with muffin liners to prevent sticking.
In a mixing bowl, combine the egg replacer with the milk, mashed bananas, nut butter, melted coconut oil, and vanilla extract. Stir until well incorporated.
In another bowl, mix together the oats, baking powder, ground cinnamon, and salt, ensuring there are no lumps.
Add the dry ingredients to the wet mixture and stir until just combined. Be careful not to overmix.
Fold in any optional ingredients like chopped nuts, dried fruit, or mini chocolate chips.
Scoop the mixture into the prepared muffin tin, filling each cup about ¾ full. Bake for 20-25 minutes until golden brown and a toothpick inserted comes out clean.
Allow the oatmeal cups to cool in the tin for a few minutes before transferring to a wire rack to cool completely. Enjoy warm or store for later!