In a saute pan, whisk the gravy, horseradish and cream together, over medium heat. Cook the sauce for 4 to 5 minutes. Season with salt and pepper. Mound the roasted potatoes in the center of the plate. Carve the brisket and lay over the potatoes. Spoon the sauce over the meat. Garnish with fried shallot crusts, chives and peppers.