Add the oil and the onion to a large heavy-based saucepan and set it over a medium heat. Once the onion starts to sizzle, cook for about 5 minutes until it starts to soften. Add the garlic and cook for another 2 minutes until the garlic has softened. Meanwhile, cut the chorizo into small cubes.

Add the chorizo to the pan and fry for 6 to 8 minutes until the oil has started to come out of the chorizo and it has gone a little crispy around the edges.

Open the beans into a sieve and rinse under a cold tap. Add them to the pan, along with the stock, tomatoes, oregano, Worcestershire sauce, mustard, balsamic vinegar, sugar and a good few grinds of salt and pepper. Stir well and reduce the heat to low. Allow to simmer without a lid for 30 minutes, stirring occasionally.