Cut the pork shoulder into 2-inch cubes. Add the pork to the bowl of the slow cooker.
Step 2
Add the chipotles in adobo, pineapple, red onion, chili powder, lime juice, white vinegar, salt, cumin and black pepper to a blender or food processor. Puree until the mixture is completely smooth, about 30-60 seconds. Stir in the beer until it is evenly combined. Then pour the mixture on top of the pork, and toss until the pork is evenly coated.
Step 3
Cook on low for 8-10 hours, or on high for 4-5 hours, until the pork is completely tender and shreds easily with a fork. Use two forks to shred the pork, then toss it in the remaining juices.
Step 4
Serve warm on tortillas, garnished with optional toppings.