Ham, Carmelized Onion, & Cheese Panini

1 large Onion, thinly sliced
1/4 tsp Sugar
4 tsp Dijon Mustard
3 tsp Horseradish
2 tsp Honey
Sliced Bread, with thin layer of butter spread on one side
9 oz. sliced Honey Ham (sandwich meat)
6 slices thin sliced Swiss Cheese

1. Cook onions and sugar in a sprayed pan for about 10 minutes on medium until lightly browned.
2. Mix mustard, horseradish, and honey; Spread onto 6 slices of bread. (Leave butter on the "outside")
3. Layer each with 3 slices of ham, 2 Tbsp onions, and 1 slice cheese, top with bread (Once again, with the butter on the "outside").
4. Cook on skillet or in panini grill.

I am craving this just thinking about it!