Preheat grill or grill pan.
Place tortillas on a cutting board. On half of each tortilla place the cheese, apple, onion, and chicken. Fold the top half of the tortilla over and place on the grill. Grill for 2 to 3 minutes on each side until the cheese has melted and the filling is warm. Cut each quesadilla into 4 triangles. Garnish with Peanut Sauce and sour cream.
Peanut Sauce:
1 cup peanut butter
3/4 cup hot water
1/8 cup molasses
1 teaspoon soy sauce
1/4 teaspoon cayenne pepper
1/4 teaspoon sugar
1/8 teaspoon salt
1 tablespoon lemon juice
In a mixing bowl, whisk together all ingredients until smooth. Store leftover peanut sauce in an airtight container in the refrigerator for up to 1 week.