Heat stock in a large pot. Bring to a simmer while you start cooking the lamb shanks.
Using a large deep pan (preferably a rondeau), Heat a little olive oil over high heat. Put the lamb shanks in the oil and brown well. Cook about 5 minutes on one side, then turn and do the other side for another 5 minutes. You want a good caramelization.
Add the vegetables and garlic. Cook for a couple minutes until softened, stirring as needed. Then add the rosemary and bay leaf.
Add the red wine and bring to a boil. Cook down until half the volume of the liquid is gone.
Add the stock. Bring to a boil, then taper back to a simmer. Cover the pot. You want the liquid lightly bubbling, but not rolling. Let it cook over low heat for about an hour. Check the tenderness of the lamb shanks. They should have some give, but, not fall off the bone. Continue cooking until they are done. Depending on the temperature, this can take up to 2 hours.
When the meat is tender enough, it will yield to a fork. Remove from the liquid. Then strain the liquid to remove the vegetables and make a smooth sauce. Return the sauce to a pot and reduce until it thickens. It should thicken naturally from the collagen in the sauce. If it is still too thin, take about a tablespoon of cornstarch, mix it with cold water, then whisk it into the sauce to thicken. Then season. You are ready to serve. Place the lamb on a plate with a good lip. Ladle the sauce over and top with charoset. Serve with potatoes and vegetables.
