Blanch the cleaned and quartered cauliflower in boiling salted water for about 5 minutes. Then quench with ice water and drain well. Roughly cut out the stalk and divide into florets. Pre-cook the macaroni for approx. 5 minutes, then drain. Cut the ham into large cubes.
Put cauliflower, macaroni and ham in a greased casserole dish and mix or layer together.
Make a light roux from butter and flour, deglaze with milk. Melt the cheese in it. Season the sauce with salt, pepper and nutmeg and spread over the casserole ingredients.
Cook in a preheated oven (220 degrees) for approx. 20 minutes.