Into a large mixing bow add flour, baking powder, sugar, salt and mix well.
Grate the cold butter and add it to the flour mix. Alternatively, you can cube the butter and add it to the flour, but grating integrates much more easily.
Gently mix the butter into the flour until it's crumbly.
Gradually add the milk into the mix, working it until a loose dough forms. Don't overmix. It's OK to have some pieces of butter in the dough.
Transfer the dough to a floured surface and spread the dough into a rectangle. Fold the dough twice then spread it into 1½ inch thickness using your hands. You can use a rolling pin gently on the top to get an even layer.
Use a biscuit cutter or a cookie cutter to cut 6 biscuits. Spread the remaining dough and cut another 2 biscuits.
Preheat air fryer at 380 degrees F for 2 minutes. Place the biscuits in the air fryer basket and air fry for 8 to 10 minutes. Until the biscuits have risen and the tops are golden brown. You'll have to work in batches.