Wash, quarter, seed and dice the tomatoes. Grate cheese finely. Peel onion. Dice 1 finely. Heat 2 tablespoons of fat in a saucepan, fry diced onion in it. Dust with flour and sweat for about 1 minute.
Add stock and cream and mix well with a whisk. Bring to the boil and simmer for about 10 minutes. In the meantime clean, wash and cut the leek into pieces of about 12 cm. Cook for about 8 minutes in boiling salted water, remove and chill. Peel and wash the potatoes and cut them into smaller pieces. Cook in boiling salted water for about 15 minutes. Halve the ham and wrap one half around a leek stick. Put them into an ovenproof casserole dish and sprinkle diced tomatoes on top. Remove the sauce from the heat and stir in 50 g of cheese. Season with a little salt and cayenne pepper. Pour the sauce over the leeks and sprinkle the rest of the cheese on top. Gratinate in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 10-12 minutes.
Put them into an ovenproof casserole dish and sprinkle diced tomatoes on top. Remove the sauce from the heat and stir in 50 g of cheese. Season with a little salt and cayenne pepper. Pour the sauce over the leeks and sprinkle the rest of the cheese on top. Gratinate in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 10-12 minutes. Cut remaining onion into rings. Heat 1 tablespoon of oil in a pan and fry the onion rings until golden brown. Drain the potatoes, put them back into the pot and mash them. Gradually stir in milk and 25 g fat. Season with salt, pepper and nutmeg. Take out the casserole. Add mashed potatoes sprinkled with onion rings
Heat 1 tablespoon of oil in a pan and fry the onion rings until golden brown. Drain the potatoes, put them back into the pot and mash them. Gradually stir in milk and 25 g fat. Season with salt, pepper and nutmeg. Take out the casserole. Add mashed potatoes sprinkled with onion rings