Gather all the ingredients. Preheat the oven to 350ºF (180ºC).
Cut the meat into 5-inch (13 cm) chunks and generously season with salt and pepper.
In a large Dutch oven, heat oil on medium-high heat. Place the pork in a single layer without overlapping each other. If your pot is small, cook in batches to avoid steaming the meat.
Cook the meat till brown without flipping too often. When all sides of the meat are nicely seared, transfer to a plate and set aside.
Lower the heat to medium and add the onions to the pot.
Sauté onions until tender and then add garlic to cook for 2 more minutes.
Add the beer.
Scrape off all the delicious brown bits on the bottom of the pot with a wooden spoon.
Add the pork back to the pot.
Add all the seasonings.
Mix all together.
Braise in the preheated oven, uncovered, for about 2 ½ hours, turning the pork every half an hour during cooking.
When much of the liquid is evaporated and the pork is falling apart, remove the pot from the oven. Take the pork pieces out to the plate so they will cool down.
When the meat is cooled down, shred them into bite sizes with your hand. Serve with corn or flour tortillas and your choice of salsas and toppings.
To Store
You can keep the leftovers in an airtight container and store in the refrigerator for up to 4 days or in the freezer for a month.