Clean and wash the leeks and cut them into pieces of about 5 cm. Blanch the leeks in bubbling salt water for about 5 minutes, then rinse in cold water and drain on a sieve.
Melt the fat in a pot and stir in the flour. Deglaze with vegetable stock and cream and bring to the boil while stirring. Stir in processed cheese and egg and season to taste with salt, pepper and nutmeg. Wrap the leek in slices of ham, place them in a greased casserole dish in a pyramid shape and pour the sauce over them.
Bake in the preheated oven (electric cooker: 200°C/ convection oven: 175 °C/ gas: level 3) for approx. 15 minutes. Cook rice in plenty of boiling salted water. Wash tomatoes, dab dry, quarter, seed and cut into cubes.
Wash the parsley, dab dry and cut into strips, except for something to garnish. Mix the rice with the diced tomatoes and parsley. Put the rice on plates, with the leek gratin