1. Place 4 of the waffles on a work surface. Spread one side of each with the mustard (if using
2. Top with the ham, cheese, and remaining waffles. Spread the top of each sandwich with 1/2 tablespoon of the butter
3. Melt the remaining 2 tablespoon butter in a large non-stick skillet over medium heat. Add the sandwiches, buttered-side up.
4. Cook, pressing occasionally with the back of a spatula, until the cheese melts and the waffles are golden. 3 to 4 minutes on each side.