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 bananas until smooth. Whisk in the melted butter and brown sugar until well combined.
03 - Add the eggs, milk, and vanilla extract to the banana mixture. Whisk until smooth and fully incorporated.
04 - In a separate 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 until just combined. Do not overmix to maintain tender texture.
06 - Spoon or pipe the batter evenly into the prepared donut pan, filling each cavity about 3/4 full.
07 - Bake for 10–12 minutes, or until a toothpick inserted into a donut comes out clean.
08 - Remove from oven and let cool in the pan for 5 minutes, then transfer to a wire rack to cool completely before glazing.
09 - In a small bowl, whisk together powdered sugar, milk, and vanilla until smooth. Drizzle or dip cooled donuts in glaze.