Place pork shoulder in slow cooker and add cumin, onion, jalapeno, beer, apple cider vinegar, chipotle peppers, salt and pepper. Cut one orange and one lime in half and squeeze the juice into the slow cooker. Throw in the squeezed orange halves. Cook on high heat for about 4-5 hours, or until meat is tender and falling off the bone.
Remove the pork from the slow cooker and place on a large baking sheet. Use a fork to shred it. Spread it out in an even layer and drizzle it with orange juice from the second orange. Season with additional salt if required.
Place it under the broiler for about 5 minutes. Remove and stir. Broil for another 5 minutes and stir. Repeat the process 4-5 times until the pork carnitas is crisp around the edges. Broil more or less depending on preference.
Serve meat with tortillas, orange and lime juice, diced onions, avocado and cilantro. If you would like some spice, add your favorite salsa or some diced peppers.
For a soft, pliable corn tortilla, heat 1 tablespoon of oil with 1 tablespoon of the cooking liquid in a skillet. Fry the tortilla until soft and lightly browned, about 1 minutes per side. Continue with remaining tortillas.
Use a slow cooker with a timer so you can set it and forget it while you're at work.
I highly recommend using a fatty cut of pork like the shoulder - this keeps the carnitas moist while cooking.
Broil for as little or as much as you need to depending on the desired crispness. I like a carnitas with crispy caramelized pieces so I usually broil it longer.
Corn or flour tortillas can be used.
Fry the tortillas in a mixture of the cooking liquid and oil to make them more pliable.