Prep the pan and oven. Line a 12-cup muffin tin with liners and heat the oven to 350°F (175°C). This ensures even baking and easy cleanup.

Mash the bananas. In a large bowl, mash the bananas until mostly smooth with a few small lumps. You should have about 1 1/4 cups of mashed banana.

Whisk the wet ingredients. Add granulated sugar, brown sugar, melted butter, oil, eggs, sour cream, and vanilla to the bananas. Whisk until well combined and glossy.

Combine dry ingredients. In a separate bowl, whisk flour, baking powder, baking soda, salt, and cinnamon. This helps distribute leaveners evenly.

Bring it together. Add the dry mixture to the wet ingredients. Stir gently with a spatula just until no dry flour remains. Do not overmix. Fold in any add-ins.

Fill the liners. Divide the batter among the 12 liners, filling each about 3/4 full. The batter should be thick but spoonable.

Bake. Bake for 17–20 minutes, or until the tops spring back lightly and a toothpick comes out with a few moist crumbs. Avoid overbaking.

Cool completely. Let cupcakes cool in the pan for 5 minutes, then transfer to a wire rack to cool completely before frosting.

Make the frosting (optional). Beat cream cheese and butter until smooth and fluffy. Add powdered sugar gradually, then vanilla and a pinch of salt. Beat until spreadable. Adjust sweetness to taste.

Frost and finish. Swirl frosting over cooled cupcakes. Sprinkle with chopped nuts, a dusting of cinnamon, or mini chips if you like.