Peel the onion, garlic, and potatoes. Wash the potatoes and cut them into small cubes. Dice the onion and garlic.
Heat two tablespoons of oil in a pan. Add the ground beef and fry. Add the onion and garlic. Pour the tomato sauce on top and season. Set aside.
Heat two tablespoons of oil in another pan. Fry the potato cubes for 12 to 15 minutes. Season at the end.
Cut the puff pastry into a circle and place it in a round baking dish, covering the base and sides.
Break up 7 oz of feta and stir it into the sour cream and eggs to form a smooth mixture. Season with salt and pepper.
Cut the remaining feta into cubes, the tomatoes into halves, and the pepperoncini into rings.
Preheat the oven to 390°F. Spoon the ground beef and potatoes onto the pastry. Pour the feta and egg mix on top. Add the feta cubes, cherry tomatoes, pine nuts, and pepperoncini on top. Fold any overhanging pastry over the filling.
Bake on the lowest rack in the oven for about 40 minutes. Optionally, add pine nuts after 30 minutes of baking. Serve hot.