Boil the potatoes in salted water for about 20 minutes
Wash the fennel and cut into slices (leek into rings). Possibly chop fennel green. Steam fennel slices covered in vegetable stock for about 10 minutes
Wash and halve the tomatoes. Lift the fennel out of the stock. Pour milk into the stock, bring to the boil and thicken. Add cheese and melt in it. Season to taste with pepper and salt if necessary
Heat fennel slices and tomato halves in the sauce. Wash the chives and cut into fine rolls
Drain the potatoes. Serve with vegetables and cheese sauce. Sprinkle with chives and possibly fennel green