Place oven rack in center of oven and preheat broiler. Season the chicken with salt and pepper. In a 12-inch oven-safe skillet, heat the oil on high. Add chicken and cook 5-6 min., flipping halfway through, until light golden brown. Remove from heat and transfer seared chicken to a plate.
Add the spinach to skillet and warm 1 min., stirring, until slightly wilted. Top spinach with chicken and any juices from plate. Spread the artichoke dip evenly on top of chicken and lay the mozzarella slices over whole skillet. Broil skillet 3-4 min., until cheese is bubbly and chicken is cooked through.
Tip: Serve with pasta, rice, or mashed potatoes.