- To make lamb marinade, use a shallow dish to mix the garlic, rosemary, mustard, red wine, salt, and pepper. Add lamb and let marinate 2 to 8 hours.
- Preheat oven to 375
- Make sauce by combining all ingredients; season to taste.
- Remove lamb from marinade and bring to room temperature.
- Heat 1 tablespoon olive oil in Dutch oven or large cast iron skillet. Add lamb and sear on both sides until brown.
- Transfer skillet to oven and roast for 15 minutes for medium rare. Remove from oven and rest 5 minutes. Pour sauce over rack and serve.