In a small bowl, mix together, cheese, mayonnaise and Dijon. Mix well. Spread cheese mixture on each piece of bread, dividing evenly.
Divide ham into fourth's place on one piece cheese slathered bread then top with second bread slice.
In a shallow dish, whisk together eggs, cream and nutmeg. Carefully dip each sandwich into egg wash coating well on both sides.
Heat 2 Tbsp butter in a non-stick skillet over medium-high heat. Cook two sandwiches at a time for 2-3 minutes on each side until golden. Add more butter between batches.
Serve immediately dusted with powdered sugar and preserves.
Notes
I recommend using one of those fluffy, inexpensive loaves of Italian bread from the grocery store bakery for these sandwiches. It isn't always even from end to end so, pair like size pieces together before you start. You may also use Texas toast.
You can substitute Gruyere or Fontina cheese in place of Swiss, if desired.