This is my grandmother's recipe.
1 1/2 cups flour
1 1/2 teaspoons baking powder
4-5 ounces butter
Sift flour and baking powder.
Rub butter into flour until like coarse breadcrumbs.
Mix in enough water to make a cohesive dough (try 1/2 cup at first).
(Chill for half an hour in fridge if you can be bothered!)
Then roll our to fit your pie dish.