Preheat convection oven to 190C.
Using a pastry cutter or knives, cut the butter into the flour/salt/baking powder mixture until it is sandy in texture.
Add grated cheese and stir.
Add milk gradually, stirring, until the texture is like play-dough or dryish modeling clay.
On floured parchment paper, flatten the dough with hands until about 2 cm thick; fold in half; repeat 5-10 times, adding flour to keep from sticking, so the biscuits get flaky.
Punch out biscuits using a small glass (dipped in flour after each punch); place 3 cm apart on a baking sheet with parchment paper.
(You can rework the leftover dough and punch out more biscuits so there is no waste).
Bake for 10 minutes or so, until golden brown.