Clean, halve and wash the chicory. Blanch in boiling salted water for 2-3 minutes. Drain, rinse with cold water and drain well. Wrap 1 slice of ham around each chicory half.
Place in a casserole dish. For the béchamel sauce, melt the fat in a saucepan. Dust with flour and sauté briefly while stirring. Gradually add milk and 350 ml water. Bring to the boil, stir in the stock and simmer for 5 minutes.
Gradually add 50 g cheese and let it melt. Season to taste with salt, pepper and nutmeg. Pour béchamel over the chicory. Sprinkle with 25 g cheese. Bake in the preheated oven (electric cooker: 200 °C/ convection oven: 175 °C/ gas: level 3) for 20-25 minutes.
Clean, wash and cut the spring onions into rings. Sprinkle over the casserole 5 minutes before the end of cooking time.