Preheat a panini grill, George Foreman style grill, or non-stick pan on the stovetop over medium heat.
Mix the mustard and honey in a bowl and spread inside both slices of bread. Layer with cheese, spring mix, ham, tomato seasoned with salt and pepper, and more cheese.
Lightly grease the panini style grill (or non-stick pan with a lid) with the non-stick spray. Grill the sandwich until the cheese is melted and the bread is golden brown on both sides.