In a 6-qt. slow cooker, combine cauliflower, soup and cheese. Cook, covered, on low for 5-6 hours or until cauliflower is tender. Stir in sour cream, salt and pepper., In a small skillet, melt butter over medium heat. Add bread crumbs; cook and stir until golden brown, 2-3 minutes. Sprinkle over cauliflower.