Roll out pastry to line dish. Boil or steam chopped potatoes.
Sauté the chopped onions in oil until cooked. Then combined cooked potatoes and onions add garlic, milk, butter and half the cheese.
Season and leave to cool. Once cool fill the pastry case and sprinkle with remaining cheese.
Bake in the oven at 220C/200C Fan/ Gas 7 for 20 minutes or until golden.