Ingredients
1 1/2 cups coarsely grated aged cheddar (4 1/2 ounces)
1 1/2 cups coarsely grated aged Swiss (5 ounces)
5 teaspoons freshly grated horseradish, or prepared horseradish to taste
3 pounds grass-fed ground beef chuck (85 percent lean)
Coarse salt and freshly ground pepper
Safflower oil, for brushing
1/2 cup mayonnaise
3 tablespoons ketchup
8 brioche buns, split
4 tablespoons unsalted butter, melted
8 slices (1/4-inch-thick) large, ripe red tomato
16 slices crisp-cooked bacon (1 pound)
8 small lettuce leaves
Bread-and-butter pickle slices
Preparation
Preheat grill to medium. Combine both cheeses and horseradish. Gently form beef into 8 patties, each about 4 inches in diameter. Season generously with salt and pepper. Brush grates with oil; grill burgers 4 minutes. Flip; top each with just over 1/4 cup cheese mixture. Cover grill and cook, about 4 minutes more for medium-rare. Remove burgers from grill; let rest 5 minutes before assembling.
Combine mayonnaise and ketchup. Brush split sides of buns with butter; grill until lightly toasted. Season tomato with salt and pepper. Sandwich burgers in buns with mayonnaise mixture, tomato, bacon, lettuce, and pickles.
