Place the oxtail in a large bowl and cover with cold water. Soak, refrigerated, for at least 8 hours or overnight.
Drain the meat, rinse with cold water, and place in a heavy-bottomed pot. Add the bay leaves, peppercorns, and the green tops of the leek. Add enough cold water to cover the meat, plus 2 inches. Place the pot over medium heat and gradually bring it