Pat the pork dry with paper towels and sprinkle with salt and pepper. In a large Dutch oven, heat the canola oil over high heat. Working in batches so as not to overcrowd the pan, cook the pork for 3-4 minutes, until browned all over. Use a slotted spoon to transfer to a large bowl. Reduce the heat to medium. Add the onions, and cook until soft, 5-7 minutes. Stir in the garlic, cumin, oregano, and bay leaves. Cook for 1 minute, then increase the heat to high and add the apple cider vinegar. Scrape up any browned bits from the bottom of the pan. Pour in the chicken stock and add the reserved peppers and tomatillos. Bring to a boil, then reduce the heat to low, cover, and simmer until the pork is tender, 2 -2 1/2 hours. Add the diced potatoes, and cook an additional 30-40 minutes, until they are tender. Season to taste with more salt and pepper.