1. Preheat oven to 350 degrees Fahrenheit.
2. Heat a braiser over medium heat. Add onions, stir frequently, and sauté until golden, about 10 minutes. Add onion soup mix, salt and pepper. Deglaze the pan with stock, scraping all the stuck-on bits (loads of flavor in there). Add the silan and bring to a boil. Add the garlic and roast; spoon sauce over the meat. Cover and transfer to the oven.
3. Cook low and slow for 90 minutes. Carefully remove from the oven and flip the meat over. Return to the oven and cook another two hours. Slice and spoon sauce extra sauce over each slice.