1 large head celery root, peeled, halved, and cut into 1/4-inch wedges
2 large carrots, thinly sliced (about ¼”)
2 boneless rib eyes (1 pound each; 1 1/4 inches thick), excess fat trimmed
Salt and pepper
1 tablespoon unsalted butter, room temperature
2 teaspoons prepared horseradish
1 teaspoon Dijon mustard
1/4 cup sliced fresh chives

Heat broiler, with rack 8 inches from heat. On a rimmed baking sheet, toss celery root and carrots with oil and arrange in an even layer. Pat steaks dry and add to sheet; season vegetables and steaks with salt and pepper. Broil until vegetables are tender and steaks are browned, 8 to 10 minutes, flipping vegetables halfway through. Tent steaks with foil and let rest 10 minutes. Stir together butter, horseradish, and mustard; season with salt and pepper and spread on steaks. Sprinkle with chives to serve.