First make the stuffing. Heat a little olive oil in a large frying pan, add the chorizo, and cook for about 3 minutes, until turning golden. Add the onion and cook for a minute or two until softened, then add the garlic. Cook for an additional couple of minutes before adding the leaves from 3 thyme sprigs. Stir in the cannellini beans, seasoning well. Cook for a minute or two to warm through. Add the tomatoes and a couple of tablespoons of the oil they are stored in. Stir to combine, then remove from the heat and cool.