Boil potatoes until soft and put through a ricer. Heat cream and butter together. Mix potatoes together with cream mixture, horseradish, cheese and eggs. Season with salt and pepper. In a 2-ounce muffin tin apply the cooking spray and coat with Panko. Pour potato mixture in and bake in a 350ºF oven for 25 minutes, or until a toothpick comes out clean. When soufflés are done, invert onto a clean cutting board and serve.