Peel, wash and cut the potatoes into large pieces. Cover and cook in salted water for about 20 minutes. Clean and wash the cauliflower and cut into florets. Cover and cook in a little boiling salted water for about 6 minutes.
Dice ham, peel and dice onions. Drain the cauliflower, collect the cooking water and fill up to 1/4 l with water if necessary.
Melt 2 tablespoon butter, sauté the onions in it, sweat the flour briefly. Stir in the cauliflower boiling water, milk and granulated broth and bring the sauce to the boil, simmer for about 5 minutes and season with salt, pepper and nutmeg.
Drain the potatoes, spread them with the ham and cauliflower in a baking dish and pour the sauce over them. Bake in a preheated oven (convection oven 175 degrees, electric stove 200 degrees) for about 30 minutes. Crumble the toast and spread it with 1 tablespoon of butter in flakes after about 20 minutes of baking time on the casserole.