In a large mixing bowl combine chicken thighs with Montreal Chicken Seasoning with olive oil. Refrigerate meat for 1 hour. In a mixing bowl combine apple and mayonnaise. Set aside. Grill chicken thigh cutlets over medium-high heat for 3 minutes per side or until internal temperature reaches 165°F (74°C). Place Brie cheese on cooked chicken thigh and rest for 2 minutes. Assemble sandwich in the following order: bun (bottom) chicken thigh apple salad and bun (top).