Place the beef tongue along with the onions, garlic, Jalapeno pepper, red pepper flakes, peppercorns and bay leaf in a pot or dutch oven.
1 beef tongue, 2 onions, 2 cloves garlic, 1 Jalapeno pepper, A pinch of red pepper flakes, 4 whole peppercorns, 1 bay leaf
Pour in enough of the stock to cover the tongue completely and season to taste with sea salt and freshly ground black pepper.
Chicken or beef stock to cover, Sea salt and freshly ground black pepper to taste
Bring to a boil, then reduce to a simmer and simmer, covered for about 3 hours, until very tender.
Remove the tongue from the liquid and let cool until it can be handled while keeping the liquid on a low heat so it stays hot.
Once cool enough, peel the skin off the tongue, slice and serve with the hot liquid.