Heat oven to 450°F Rub or grate 1.75 oz. of very cold butter into flour. Add 1/2 grated cheese, 1/2 t. salt, then add 2 - 3 tablespoons of cold water drop by drop until the dough partially sticks together to form a ball.
Roll pastry thinly to line a 23 cm (9") pie plate or flan tin. Chill until filling is ready.
Cook 2 - 3 rashers of bacon into a large frying pan. Add 1 tablespoon butter and 1 chopped onion. Cook over moderate heat until onion is lightly browned and transparent.
Chop 3 large boiled new potatoes into this mixture and turn until the potatoes are warmed through, and are coated with bacon fat. In the bowl in which the pastry was mixed, break 3 or 4 eggs. Add 1 tablespoon milk for each egg, then add 1 teaspoon salt. Mix with a fork to blend whites and yolks, then add potato mixture from pan. Stir to mix, then tip filling into the chilled pie crust.
Sprinkle surface with grated cheese and paprika and bake at 450 F for 20 minutes or until pastry is golden brown and the eggs have set.
Serve warm, cold, or reheated alone or with salad.