Puree (mortar and pestle) 1 tbsp oil with the vinegar, turmeric, cumin, peppers, whole garlic, and salt to make a thick paste
Place chicken in large casserole, rub in the paste, cover overnight.
Scrape marinate off the chicken, save.
Heat remaining oil in casserole, brown chicken in batches, 5 minutes per side till brown. Remove.
Add remaining garlic, 20 seconds. Add onions, scraping up brown bits, about 8 minutes. Add marinate, tomatoes, cilantro until soft, about 5 minutes.
Add liquor off the heat, return until evaporated, 2 minutes.
Add chicken to pot with the potatoes and chicken stock, season with salt and pepper. Cover and simmer over low heat until potatoes are tender, about 35 minutes.
Serve with rice.