1. To make the marinade: Mix together garlic, salt, pepper, and olive oil in a small bowl. Add whiskey, liqueur, cocoa powder, and soy sauce. Combine well.
2. Place roast in a large pan. Smear marinade mixture all over meat. Sprinkle with crushed bay leaf. Cover and refrigerate overnight.
3. Cut onion into quarters and slice crosswise. Heat olive oil in an eight-quart pot. Add onion slices and sauté for five minutes, stirring occasionally. Add the light brown sugar and mix together for one minute.
4. Add the roast to the pot together with the liquid from the marinade. Do not add any water. Bring to a boil, reduce heat to low, and cook for three hours or until soft, rotating roast every hour. It’s important to cook over low heat so the meat releases its own juices.
5. When it’s finished cooking, leave the meat in the covered pot, with the flame off, for half an hour. Remove from pot, cool to room temperature, and then refrigerate for a few hours before slicing.
Freeze the sliced roast and gravy separately. When ready to use, defrost both, then pour the gravy over the meat and heat in the oven, or in a pot on the stovetop.