Heat canola oil in a large skillet over medium-high heat. Sprinkle chicken with salt and pepper. Sauté 3 minutes on each side or until done. Let stand 10 minutes. Slice chicken; toss with garlic.
Spread spicy brown mustard over bottom half of bread; top with Havarti cheese, ham, and chicken. Sprinkle chicken with chopped pickle; cover with top half of bread. Return pan to medium heat; coat with cooking spray. Add sandwich to pan; top with another heavy skillet to weigh down. Cook 2 minutes on each side or until toasted. Cut sandwich crosswise into 4 equal portions.