Preheat your oven to 300°F (150°C). In a large Dutch oven, heat two tablespoons of olive oil over medium-high heat. Season the boneless chuck roast and short ribs generously with salt and pepper, then sear them in the hot oil until browned on all sides, about 3-4 minutes per side.

Once the meat is browned, add roughly chopped onion, crushed garlic, dried ancho chiles, guajillo chiles, and chopped Roma tomatoes to the pot. Pour in two cups of beef broth, a splash of apple cider vinegar, and toss in a couple of bay leaves. Cover the Dutch oven tightly and bake for 3-4 hours, or until the meat is fork-tender.

When cooking time is up, carefully remove the pot and let it cool for 10 minutes. Extract the meat using tongs, shred it with two forks, and blend the leftover sauce until smooth. Return it to the pot with the shredded meat.

Warm the burrito-size tortillas in a skillet or microwave. Lay a tortilla flat, add birria meat, cooked white rice, guacamole, black beans, shredded mozzarella, diced white onion, and fresh cilantro. Roll tightly, tucking in the sides.

In a large skillet over medium heat, add olive oil and place assembled burritos seam-side down, cooking for 1-2 minutes per side until golden brown.

Serve the cooked burritos warm with leftover birria sauce for dipping.