In a large Dutch oven over medium high heat, add the oil. Season the shanks on all sides with salt and pepper. Placing 2 shanks at a time, brown on all sides, about 3 minutes a side. Remove the browned shanks to a plate and repeat. Then season the lamb necks the salt and pepper and brown like the shanks. Once finished, drain the half of the fat from the pot. Add the shallots and onions, turning the heat down to medium, stir often. After the onions are just starting to brown lightly, about 8 minutes, add the leeks, carrots and fennel, cooking for another 5-6 minutes. Add the garlic, rosemary, thyme and parsley, then deglaze with the beer. Once all the fond is removed from the bottom of the pot, nestle the shanks and necks into the sautéed vegetables. Add enough cold water to cover the meat and vegetables by 1 inch. Lightly season with salt, then cover with a lid and bring the liquid to a simmer.