A quesilla (not to be confused with a quesadilla) is a hot toasted sandwich of melted Mexican string cheese, ham, avocado, onion, tomato, and jalapeño peppers. Mexican string cheese, also known as Oaxacan cheese, is similar to mozzarella cheese in color and texture but has a saltier flavor. You can substitute mozzarella or other string cheese if you wish.
2 hard rolls
2 slices ham
1 cup shredded Mexican string cheese (or mozzarella), packed
2 pickled jalapeños, seeded and halved
1 medium onion, peeled and sliced
1 medium tomato, sliced
Slices of avocado
1. Split each roll open. Top each bottom half with equal amounts of ham, cheese, jalapeño, onion, tomato, and avocado slices. Top with the remaining roll halves.
2. In a heavy cast iron skillet or grill pan, heat 1 or more tablespoons of butter over low heat until the butter hast melted. Grill each sandwich for 30 or more seconds on each side, while pressing down with a spatula or another skillet for added weight. The sandwiches are ready when the bread has browned and the cheese has softened and is just starting to melt.