1 In a 5L pot, heat two teaspoons of the oil on medium. Add the chorizo (if using) and cook until it has rendered its fat; about five minutes. Remove it to a bowl with a slotted spoon.
2 Working in two batches, add the meat to the pan and cook until browned; about five minutes per batch. Transfer with a slotted spoon to the bowl with the chorizo.
3 Add the onion, garlic and remaining two teaspoons of the oil and cook, stirring frequently, until the onion is tender; about seven minutes. Stir in the chilli powder and oregano, and cook for one minute. Stir in the tomato paste and vinegar.
4 Return the meat and chorizo to the pot along with 11/4 cups of water and the salt, and bring to a boil. Reduce to a simmer, cover and cook, stirring occasionally, until the meat is tender; about one hour. Stir in the polenta and simmer until lightly thickened; about five minutes.