Preheat the Oven: Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or grease it lightly.
Mash Bananas: In a large mixing bowl, mash the ripe bananas with a fork until smooth.
Combine Wet Ingredients: Add the melted butter, brown sugar, granulated sugar, eggs, and vanilla extract to the mashed bananas. Mix well until the ingredients are thoroughly combined.
Incorporate Dry Ingredients: In a separate bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg. Gradually add these dry ingredients to the wet mixture, stirring until just combined. Be careful not to overmix.
Add Carrots (and Nuts/Raisins): Gently fold in the grated carrots. If you're opting for an extra layer of texture and flavor, add chopped nuts or raisins to the batter.
Fill Muffin Cups: Spoon the batter into the prepared muffin cups, filling each about two-thirds full.
Bake: Bake in the preheated oven for 18-20 minutes or until a toothpick inserted into the center comes out clean.
Cool and Enjoy: Allow the muffins to cool in the tin for a few minutes before transferring them to a wire rack to cool completely. Enjoy these moist and flavorful Carrot and Banana Muffins with a cup of your favorite beverage!