Add in sliced onion, smashed garlic, and sliced ginger, and sauté until fragrant. Stir frequently so the garlic does not brown too quickly.
Add the soy sauces, Shaoxing wine, rice vinegar, water, rock sugar, white pepper, and Chinese five spice powder into the same pot.
Add beer and bring to a boil. Once boiling, lower heat to simmer and cover pot.
Simmer covered for 1 to 1.5 hour(s). Check periodically and give the pot a stir to ensure nothing is sticking to the pot and that the liquid has not completely evaporated. When pork feel tender, remove the lid.
Continue to simmer on low with pot uncovered for 10-20 minutes or until the sauce has thickened.
Sprinkle chopped scallions as an optional topping.