Heat a small, dry frying pan over a low-medium heat. Toast the paprika, cumin, oregano, thyme and cinnamon for 30 seconds until fragrant, then set aside.
Heat a little oil in a large frying pan and sear the beef until browned on all sides (depending on the size of your pan, you may need to be this in batches). Remove from the pan and set aside.
Add the onion and garlic to the pan and cook until soft and lightly browned.
Add the blended tomatoes, stock, vinegar, chipotle paste and toasted spices. Season generously with salt and pepper.
Transfer to a blender or food processor and blend until smooth.
Return the blended sauce to the pan or transfer to a slow cooker. Add the beef and bay leaves to the pan or slow cooker.
Cook on the hob over a very low heat for 2–3 hours, or in the slow cooker for 4–5 hours on low. When cooked the beef will be very tender and shred easily.
Transfer the beef to a plate and shred it using two forks. Return to the pan and stir the beef through the sauce.
At this point, the birria can be cooled and frozen, or served immediately with the sides of your choice. If serving straight away, top with finely chopped onion and fresh coriander.
