Preheat the air fryer to 350 degrees Fahrenheit.
In a large bowl, whisk together the flour, cocoa powder, sugar, baking powder, and salt.
In a separate bowl, whisk the milk, melted butter, egg, and vanilla extract until combined.
Gradually fold the wet ingredients into the dry ingredients until a thick batter forms.
Transfer the batter to a piping bag and grease the air fryer basket.
Pipe the batter into 3-inch circles into the basket, leaving 1 inch of space between each.
Air fry at 350 degrees Fahrenheit for 5 to 6 minutes until a toothpick inserted comes out clean.
Whisk together powdered sugar, glaze cocoa powder, and glaze milk in a shallow bowl.
Remove donuts from the air fryer and allow to cool on a wire rack for 2 minutes.
Dip the top of each warm donut into the glaze and serve.