Place the pork shoulder into a slow cooker. Add the yellow onion, garlic, orange juice and zest, lime juice and zest, tomato paste, cumin, oregano, bay leaves, chipotle peppers, adobo sauce, beer, tequila, vegetable stock, salt, and pepper. The pork should be covered all most all the way by the liquid.
Cover the crock pot and cook on LOW for 7 hours.
Uncover the crock pot and transfer the pork to a cutting board. Set aside.
Pour the liquid from the crock pot through a strainer (to catch the solids) into a medium saucepan. If you like you can puree the solids and add them to the liquid or discard them. Bring the cooking liquid to a simmer over medium heat and reduce to 1 cup.
While the braising liquid cooks, use a couple of forks to shred the pork.
Once the liquid has reduced, place the pork in a serving bowl and pour the liquid over the meat. Toss the meat until coated so it's nice and moist. Serve warm.*If you want to keep the meat warm or serve it buffet style, return the shredded pork to the crock pot and toss in the liquid. Cover the crock pot and set it to WARM until ready to serve.
To make tacos, cook the tortillas in a dry skillet over medium-high heat until slightly browned. Add some carnitas to the tortillas and then top with avocado, red onion, and cojita cheese.
Notes
You can use a boneless or bone-in pork shoulder or pork butt for this recipe. If using bone-in, be sure to remove the bone from the pork once it has finished cooking. It should pull right out.