01 - Preheat the oven to 350°F. Lightly grease a 12-cavity donut pan with cooking spray or butter.
02 - In a large bowl, mash the ripe bananas until smooth. Whisk in the melted butter and brown sugar until thoroughly combined and creamy.
03 - Add the eggs, milk, and vanilla extract to the banana mixture. Whisk until the mixture is smooth and uniform.
04 - In a separate medium bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, and salt until evenly distributed.
05 - Gradually fold the dry ingredients into the wet ingredients using a spatula. Mix until just combined, being careful not to overmix to maintain tender texture.
06 - Spoon or pipe the batter into the prepared donut pan cavities, filling each about 3/4 full to allow for rising during baking.
07 - Bake for 10-12 minutes until a toothpick inserted into the center comes out clean and the tops are lightly golden.
08 - Let the donuts cool in the pan for 5 minutes before transferring to a wire rack to cool completely.
09 - In a small bowl, whisk together powdered sugar, milk, and vanilla until smooth. Adjust consistency with additional milk if needed. Drizzle or dip cooled donuts in the glaze.