Prepare the dried chillies: Place the guajillo chillies in a small bowl and cover with boiling water. Let them soak for 10 minutes until they become soft and pliable. You should be able to bend them easily without cracking. Drain and set aside.

Sear the beef: Heat the vegetable oil in a large skillet over medium-high heat until it shimmers. Working in batches so you don't overcrowd the pan, add the beef chunks and sear for 2-3 minutes per side until each piece develops a deep, dark brown crust. The sound of the sizzle should be steady but not furious. Transfer the seared beef to your slow cooker insert.

Make the sauce: In a blender, combine the soaked guajillo chillies, chipotle chillies with adobo sauce, chopped onion, minced garlic, apple cider vinegar, beef stock, cumin, oregano, smoked paprika, salt, and pepper. Blend on high for 45-60 seconds until the mixture is completely smooth and a deep brick-red colour. The aroma will be smoky and slightly tangy.

Assemble in the slow cooker: Pour the blended sauce over the beef in the slow cooker. Add the bay leaves and lime juice, then stir everything together until each piece of meat is well coated. The sauce should look thick and glossy around the beef.

Cook low and slow: Place the lid on the slow cooker and set it to low heat. Cook for 6-8 hours, or on high for 4-5 hours. After about 4 hours on low, the kitchen will fill with a warm, earthy, and slightly spicy fragrance. The beef should be fork-tender when ready — it should pull apart with minimal resistance, and the sauce will have darkened and thickened slightly.

Shred and finish: Remove the bay leaves. Using two forks, shred the beef directly in the slow cooker. Stir the shredded meat through the sauce so every strand is coated. The texture should be moist and luscious, not dry or stringy. Let it sit in the sauce on the 'keep warm' setting for 10 minutes before serving to allow the flavours to meld.