Coat a large saute pan or large stovetop grill pan with cooking spray. Season both sides of chicken with salt and black pepper. Place chicken on prepared pan and cook until golden brown on each side and cooked through.
Meanwhile, in a food processor, combine spinach, mayonnaise, vermouth, horseradish, lemon juice, and parsley. Process until blended and smooth. Season, to taste, with salt and black pepper. Spoon sauce over half of the chicken. Reserve remaining chicken for another recipe.
Serve half (2 cups) of the rice with this meal and reserve remaining rice for another recipe. Garnish with lemon wedges.