Arrange half of the crackers, flat side up, in a lightly greased 9 x 13 baking dish or quarter sheet pan.
Top each cracker with a quartered slice of cheese.
Fold ham slices over to fit on top of each cracker and top with remaining cheese slices and crackers, flat side down.
Stir together butter, dijon mustard, brown sugar, Worcestershire, onion powder, and kosher salt.
Top each cracker evenly with the mixture, about ½ teaspoon on each cracker.
Bake until lightly browned and cheese is melted and bubbly around the edges.
Let stand 10 minutes before serving.
