Cook the pasta in plenty of boiling salted water for about 7 minutes. In the meantime peel garlic and dice finely. Clean, wash and cut the leek into pieces. Cut ham into large pieces.
Drain the pasta, rinse and drain. Wash, clean and slice the tomatoes. Grate cheese finely. Heat oil in a pan and fry leek and garlic. Grease an ovenproof casserole dish (28 x 16 x 4 cm).
Put half of the pasta into the mould. Spread the leek and ham on top. Pour in the rest of the noodles. Whisk eggs, milk and stock. Season with pepper and nutmeg. Pour egg milk over the noodles.
Cover pasta with tomato slices and sprinkle with cheese. Place the casserole dish in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) and let the egg milk set for about 30 minutes.
Take out, let cool a little and cut into 4 portions. Garnish with oregano leaves.