Blend flour and butter in a food processor until breadcrumbs form.
Pulse in the egg until a dough forms and flatten into a round.
Press the pastry into the base and sides of a 20cm springform tin.
Boil potatoes for 15 minutes and cut into 3cm pieces.
Fry onions in butter and oil for 15 minutes and add garlic for 2 minutes.
Preheat the oven to 200°C.
Mix potatoes, onions, garlic, 100g cheese, parsley, spinach, and spices.
Transfer filling to the pastry, pour over cream, and top with remaining cheese.
Bake for 40-45 minutes until the pastry is crisp and golden.
Cool for 10 minutes before removing from the tin and serving.