Heat a grill pan over medium-high heat. Sprinkle chicken with salt and 1/8 teaspoon pepper. Coat pan with cooking spray. Add chicken to pan; cook 3 minutes on each side or until done. Remove chicken from pan.
While the chicken cooks, combine remaining 1/8 teaspoon black pepper, mayonnaise, and next 7 ingredients (through Dijon mustard) in a blender; process until smooth.
Cut chicken into 1/2-inch pieces. Combine chicken and lettuce in a large bowl; drizzle with mayonnaise mixture. Toss to coat. Serve immediately.