Prep the Pan and Oven: Preheat your oven to 350°F (180°C). Line a jumbo muffin tin with parchment muffin cups or lightly grease each well.

Mash the Bananas: In a small bowl, mash the overripe bananas with a fork or hand mixer until smooth. The browner the bananas, the sweeter and more flavorful your muffins will be. Set aside.

Cream Butter and Sugar: In a glass batter bowl, blend the sugar and softened butter with a hand mixer until light and creamy. This step prevents butter lumps and ensures a smooth batter. If the butter isn’t fully softened, microwave it at half power for about 20 seconds.

Add Remaining Wet Ingredients: To the creamed butter mixture, add the mashed bananas, milk, vanilla, and eggs. Mix until the batter is smooth and fully combined.

Combine the Dry Ingredients: In a separate bowl, whisk together the flour, baking soda, salt, cinnamon, and nutmeg. Whisking evenly distributes the leavening and spices so the muffins bake consistently.

Bring the Batter Together: Add the dry ingredients to the wet mixture and blend with a hand mixer just until combined. Avoid overmixing to keep your muffins soft and tender.

Fill and Bake: Divide the batter evenly among the six muffin cups. Bake for 40 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.

Cool and Serve: Let the muffins rest in the pan for 10 minutes before transferring to a rack. Enjoy them warm with butter, or allow them to cool completely for 30 minutes before eating, no butter necessary.