Trim bottoms of the sprouts, remove any dodgy looking leaves and cut each one in half.
Melt the butter in an ovenproof frypan or dish on medium heat. Saute the Brussel sprouts until they start to soften (about 4 minutes).
Crush the garlic into the pan, add the onion and ham and stir until the onion is soft and glassy (4-6 minutes).
Remove from heat. Stir cream, Schmand and mustard through the sprouts, scraping and brown off the bottom of the pan as you go. Season with salt, pepper and nutmeg. Return to low heat and bring to a simmer. Stir through half the cheese.
If your pan is not oven-safe, transfer to an ovenproof dish.
Top with remaining cheese and in the oven until the cheese is melted and golden brown, about 20-25 minutes.