Sauté the onion until lightly browned, add the garlic and sauté. Add the ground beef and cook, stirring constantly. Add the tomato, the pepper, the paprika, the saffron, the salt and mix it all together very well. Let it cook until the water evaporates.
Cook the potatoes and mash them very well, add the meat to the mashed potatoes and mix.
Put it all in a baking dish and spread well, cover with the tomato sauce and spread. Add the slices of ham then add the mozzarella slices and some oregano to taste.
Bake in a preheated oven at 180°C (356°F) until the cheese has melted.