The Ultimate St. Patrick's Day Casserole | Cooking Professionally

Ingredients

• 2 tablespoons olive oil
• 1 medium onion, chopped
• 3 carrots, chopped
• 2 pounds ground lamb or ground beef
• 1 tablespoon tomato paste
• 1 teaspoon Dijon mustard
• 1 cup chicken broth
• salt, to taste
• pepper, to taste
• 4 cups mashed potatoes, cooked
• 2 tablespoons butter, melted