1. Preheat a large skillet over medium heat. Generously butter one side of each tortilla and place butter side down in the pan.
  2. Spread ½ tbsp. Dijon mustard on the top. Top the right half of each tortilla with 1/2 cup shredded cheese, apple slices, and ham. Then gently fold the tortilla in half to form a semi-circle.
  3. Cook quesadillas until warm throughout and cheese is melted, about 5-8 minutes. Flip each quesadilla over halfway through cooking.
  4. Allow to cool slightly, then slice into wedges. Serve with additional Dijon mustard for dipping.