Prepare the dry ingredients: In a large mixing bowl, combine the flour, sugar, baking powder, baking soda, and salt. Whisk them together until everything is well blended.
Prepare the wet ingredients: In another bowl, whisk the egg, milk, oil (or melted butter), and vanilla extract. Stir in the mashed bananas until the mixture is smooth and creamy.
Combine wet and dry ingredients: Make a well in the center of your dry ingredients and pour in the wet ingredients. Gently fold them together using a spoon or spatula. Be careful not to overmix. The batter should be slightly lumpy.
Add your mix-ins: If you’re adding chocolate chips, berries, or nuts, gently fold them into the batter now.
Scoop the batter: Use an ice cream scoop or spoon to fill each muffin cup about ¾ full with the batter.
Bake: Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
Cool and enjoy: Let the muffins cool in the tin for 5 minutes before transferring them to a cooling rack. Once cool enough to handle, enjoy these delicious, homemade breakfast muffins!