In a bowl add flour, sugar, salt, baking powder and stir together. Add the cubed butter and use a fork to smush that in to the flour mixture.
Pour in your milk and stir until combined. If mix is too dry you can add 1 tsp milk until it is a nice doughy but not sticky consistency.
Sprinkle a bit of flour on a cutting board. Put dough on top and sprinkle a little flour on top of that, enough for rolling pin to not stick.
Roll it out flat, then fold it a few times and roll it out again. Use a circle biscuit cutter so each piece is the same thickness. Spray inside of basket so they don't stick.
Set inside air fryer basket with a bit of space in between each one and brush melted butter on top of each one.
Cook at 400 F for about 10 minutes. Can flip halfway to brown on both sides. Keep an eye out about minute 8 since thicknesses will vary.
Break one in half to ensure middle is no longer sticky, and cooked before consuming. Brush melted butter on top when done.