Donuts:
Preheat the oven to 350°F (175°C). Grease a donut pan with butter or baking spray.
In a large bowl, whisk together flour, cocoa powder, baking powder, baking soda, salt, and nutmeg.
In another bowl, combine melted butter, brown sugar, buttermilk, egg, and vanilla extract.
Gradually mix the wet ingredients into the dry ingredients until well combined, ensuring no flour pockets remain.
Pipe the batter into the greased donut pan, filling each cavity ¾ full.
Bake for 11-13 minutes or until the donuts are golden brown and spring back when touched.
Remove from the oven and let cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
Vanilla Glaze:
In a medium bowl, mix confectioners’ sugar, milk, vanilla extract, and a pinch of salt until smooth.
Dip each cooled donut into the glaze, then place on a cooling rack above a sheet of parchment paper to catch drips.