Peel and chop the onion. Heat 1 tablespoon butter and sauté the onion cubes for about 5 minutes. Add the tomatoes, chop with a spatula and bring to the boil. Season to taste with salt, pepper and sugar. Peel, wash and halve the potatoes and cook in boiling salted water for about 20 minutes.
Clean and wash the chicory, shake dry, cut in half lengthwise and cut out the stalk in a V-shape. Season chicory with salt and pepper. Halve the ham slices and wrap 1/2 slice around 1/2 chicory
Grate the cheese roughly. Spread the sauce in 4 small or one large flat casserole dish. Place chicory halves next to each other in the sauce and sprinkle with cheese. Bake in a preheated oven (electric cooker: 225 °C/ convection oven: 200 °C/ gas: see manufacturer) for approx. 15 minutes
Wash parsley, shake dry, pluck leaves from the stalks and chop finely. Drain the potatoes, add 2 tablespoons of butter and parsley to the pot. Swivel the potatoes in a closed saucepan so that the parsley and butter are spread over the potatoes. Arrange chicory cordon bleu and potatoes