Make the kale chips: Preheat the oven to 275 degrees F. Cut off the tough stems of the kale, then cut the leaves into 1 1/2-inch pieces. Toss the kale on a baking sheet with the olive oil and 1/2 teaspoon salt; spread in a single layer. Transfer to the oven and bake, flipping halfway through, until crisp, about 20 minutes.
Meanwhile, make the sandwiches: Combine the apple and honey mustard in a medium bowl. Spread evenly onto 4 frozen waffles and top with the ham and cheese. Cover with the remaining waffles to make 4 sandwiches.
Heat 2 tablespoons butter in a large nonstick skillet over medium heat. Add the waffle sandwiches and cook until golden, about 3 minutes per side, adding the remaining 2 tablespoons butter when you flip. Remove to a cutting board and cut the sandwiches in half. Serve with the kale chips.