Melt butter in a large skillet over medium heat. Saute ham steak until heated through and browned, about 2 to 3 minutes per side. Transfer ham steak to platter, keep warm. Add heavy cream to skillet and reduce until thick enough to coat the back of a spoon, about 3 minutes. Add mustard and simmer 1 minute. Add cooked spaetzle and toss to coat.
Top ham steak with mustard cream spaetzle.
In a bowl whisk together eggs, milk, nutmeg, salt and pepper. Gradually stir in enough flour to make a thick batter. You will probably not need all 3 cups.
Using a metal colander set over a pot of boiling, salted water, press spaetzle batter through holes directly into water.
When spaetzle are cooked through, they will float to surface, about 5 minutes. Scoop up with a slotted spoon and drain well as they cook or drain all at once.