Slice the onion thinly and mince the garlic after removing their cores.

Cut slits into the pork shoulder between the lean and fat parts, then divide into thirds. Season with salt and pepper and coat with flour.

Heat olive oil in a pan over medium heat. Add onion and garlic, cooking until the onion softens (about 4 minutes).

Push the onion to the side of the pan and add the pork. Sear until browned on both sides (about 2 minutes per side). Pour in the beer and bring to a boil.