Pat the beef chuck dry and season all over with salt and pepper. Heat the oil in a large skillet over medium-high heat. Brown the beef chunks on all sides, working in batches if needed. Transfer the browned beef to the slow cooker.
Reduce the skillet heat to medium. Add the chopped onion and cook until softened, about 5-7 minutes. Add the minced garlic and cook for one minute more until fragrant.
Stir in the chopped chipotles, adobo sauce, fire-roasted tomatoes, beef broth, cumin, oregano, and smoked paprika. Bring the mixture to a simmer, scraping up any browned bits from the bottom of the skillet.
Pour the sauce mixture over the beef in the slow cooker. Add the bay leaf and stir gently to combine. Cover and cook on low for 8 hours or on high for 4-5 hours, until the beef is very tender.
Remove the bay leaf. Carefully transfer the beef to a large bowl. Use two forks to shred the meat. Strain the cooking liquid (consommé) through a fine-mesh sieve into a separate bowl; skim and discard some of the fat from the surface if desired.
To assemble the tacos, heat a large nonstick skillet or griddle over medium heat. Dip a tortilla into the warm consommé, coating both sides. Place it on the hot skillet.
Top one half of the tortilla with a sprinkle of cheese and a portion of shredded beef. Cook for 1-2 minutes until the bottom is lightly browned, then fold the other half over.
Cook, flipping once, until the taco is golden and crispy on both sides and the cheese is melted, about 2-3 minutes per side. Repeat with the remaining tortillas and filling.
Serve the tacos immediately with small bowls of the remaining warm consommé for dipping, along with chopped white onion, cilantro, and lime wedges.