Preheat the oven to 350 degrees. Season the shanks with salt and pepper. Heat an oven safe pan over medium high heat. Add 1 tablespoon of oil to the pan. Sear the lamb on all sides. Add the carrots, onions, garlic, herbs, chili flake, and bay leaf. Deglaze the pan with sherry. Add the beef stock to the pan. Bring to a simmer, cover, and place in the oven. Cook for 2 hours or until lamb is tender. Remove the lamb and herbs from the pan. Pour the sauce and vegetables in a blender container. Blend until smooth and pour back into the pan. Add the potatoes to the pan and bring to a simmer. Cook until the potatoes are tender and sauce has thickened. Season with salt and pepper to taste. Cool the sauce to room temperature and stir in the peas.