1. Preheat Your Oven and Prepare Your Muffin Tin: Start by preheating your oven to 375 F (190 C). Line a 12-cup muffin tin with paper liners or lightly grease it with cooking spray. This ensures your muffins won’t stick and makes for easy cleanup.

2. Combine Dry Ingredients Thoroughly: In a large mixing bowl, whisk together the all-purpose flour, protein powder, granulated sugar, baking powder, baking soda, ground cinnamon, and salt. Make sure there are no lumps and the ingredients are evenly distributed. This step is crucial for consistent rising and flavor.

3. Prepare the Wet Ingredients: In a separate medium bowl, mash the ripe bananas with a fork until mostly smooth but with a few small lumps remaining for texture. Then, add the milk, melted butter, large egg, and vanilla extract to the mashed bananas. Whisk these wet ingredients together until well combined.

4. Gently Combine Wet and Dry Mixtures: Pour the wet banana mixture into the bowl with the dry ingredients. Stir gently with a spatula or wooden spoon until just combined. It’s important not to overmix; a few lumps of flour are perfectly fine. Overmixing can lead to tough muffins. If using, fold in chocolate chips or nuts at this stage.

5. Fill the Muffin Cups Evenly: Divide the batter evenly among the 12 prepared muffin cups. An ice cream scoop or two spoons work well for this, ensuring each muffin is roughly the same size and bakes uniformly. Fill each cup about two-thirds full.

6. Bake Until Golden Brown: Place the muffin tin in the preheated oven and bake for 18-22 minutes. The muffins are done when they are golden brown on top and a wooden skewer or toothpick inserted into the center of a muffin comes out clean or with a few moist crumbs attached.

7. Cool Before Serving: Once baked, remove the muffin tin from the oven and let the muffins cool in the tin for 5 minutes. Then, transfer them to a wire rack to cool completely. This prevents the bottoms from getting soggy and allows them to set properly.