Fry the chorizo in a heavy-based pan for 2-3 minutes, until just crisp and releases its fat. Transfer the chorizo slices to a plate.
Keep the fat in the pan. Add the onion, garlic and chilli, then cook gently for 3-5 minutes.
Add the thyme, chickpeas and mixed beans and put back the chorizo, then cook for a couple of minutes. Stir in the chopped tomatoes and enough stock to cover. Simmer, under a lid, for 10 minutes, then for a further 5 minutes without a lid to thicken the sauce.
Serve it with a dollop of sour-cream, if you like.