Heat avocado oil in heavy pot over medium-high heat.
Brown pork chunks in two batches until well-seared, 8-10 minutes per batch.
Return all pork to pot, add garlic powder and sliced onion, cook 3-4 minutes.
Add water, both soy sauces, rice vinegar, bay leaves, peppercorns, and brown sugar. Scrape up browned bits.
Bring to boil, reduce to low, cover and simmer 60-75 minutes until pork shreds easily.
Uncover and simmer 15-20 minutes until sauce reduces by half and thickens.
Adjust seasoning to taste with water, vinegar, or sugar as needed.
Serve over steamed rice with sauce and peppercorns.