Preheat oven to 375 degrees.
Whisk together mustard, honey, oil and garlic in a small bowl. Lay duck legs on a baking sheet with carrots and coat with marinade. Roast for 30 minutes or until duck legs are cooked through. Remove from oven. Heat about 2 Tbsp. of the duck fat in a medium sauté pan. Add mustard greens and sauté for about 2 minutes or until wilted. Season with salt and pepper to taste. Serve duck legs with wilted greens and roasted carrots.