Rub butter or margarine into the flour until the mixture resembles fine breadcrumbs. Stir in the chilli powder, onion and cheese. Carefully add enough milk bit by bit to mix to a stiff dough. It shouldn't be too wet.
Roll out the dough to about half an inch thick. Cut out circles with a scone cutter or you can make one large scone and mark segments with a knife (but don't cut all the way through if you choose to make one large scone).
Place on a greased or lined baking tray. Brush the tops with a little milk and sprinkle the chilli flakes - if using them.
Bake for 20 minutes in the centre of the oven until golden on the top and bottom.
Eat while warm spread with butter.
I prefer onions nice and soft, so I pre-cook them in the microwave in a little water. Drain well and pat dry before using in the scone mixture.