Put the onions, garlic and oil into a large saucepan over low heat. Cook the onions for 15 minutes, stirring frequently, until soft and golden.
Stir through the brisket and speck, mixing well, then add the remaining ingredients. Increase the temperature and bring to the boil. Reduce the heat to a simmer, place a lid on the pot and leave a gap for steam to escape.
Simmer for two hours, stirring occasionally, until the meat is tender and the liquid is nice and thick.