In a mixing bowl, whisk together the flour, baking powder, salt, and granulated sugar until well combined.

In another bowl, mix the milk, egg, and vanilla extract. Whisk until combined and then pour in the melted butter, mixing until fully incorporated.

Pour the wet ingredients into the dry ingredients and stir until a dough forms. Don’t overmix; it’s okay if a few lumps remain.

Lightly flour a clean surface and roll out the dough to about ¾ inch thick.

Using a biscuit cutter, cut out biscuit shapes and place them on a parchment-lined plate.

Preheat the air fryer to 350°F (175°C) for about 5 minutes.

Once the air fryer is preheated, arrange the biscuits in a single layer in the air fryer basket. You may need to cook them in batches, depending on the size of your air fryer.

Cook the biscuits for 8 minutes or until they are golden brown and cooked through.

Prepare the topping by mixing the ground cinnamon and granulated sugar together in a small bowl. Set aside.

If glazing, whisk together the powdered sugar and milk, adding more milk if necessary until you reach your desired consistency.

Once the biscuits are done, remove them from the air fryer and let them cool for a few moments.

Brush the biscuits with the glaze if desired, or sprinkle the cinnamon sugar topping over them while they are still warm.