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 well combined and creamy.
03 - Add the eggs, milk, and vanilla extract to the banana mixture. Whisk thoroughly until the mixture is smooth and uniform.
04 - In a separate medium bowl, whisk together the all-purpose 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—do not overmix as this will make the donuts tough.
06 - Spoon or pipe the batter evenly into the prepared donut pan, filling each cavity about 3/4 full to allow for rising.
07 - Bake for 10–12 minutes, or until a toothpick inserted into the center of a donut comes out clean and the tops are lightly golden.
08 - Remove from the oven and let the donuts cool in the pan for 5 minutes. Carefully transfer to a wire rack to cool completely before glazing.
09 - In a small bowl, whisk together powdered sugar, 1–2 tablespoons milk, and vanilla extract until smooth. Adjust milk consistency as needed. Drizzle or dip cooled donuts in glaze.