![Butter Pie](https://static.ooooby.org/image/recipe/npm/5e88a11e-a550-40e1-a56c-ba66bc8cd888.aafb8200.jpg)
Ingredients
For the pastry
75 grams butter
75 grams lard
350 grams plain flour
1 teaspoon fine salt
75 millilitres very cold water
For the filling
3 large potatoes (peeled and cut into slices)
120 grams butter
2 large onions (cut into slices)
salt and freshly ground black pepper
1 egg (beaten, to glaze)