In a large bowl combine sherry or red wine vinegar, spices, marsala wine with a tbsp of olive oil . Mix thoroughly and marinate chicken for at least 2 hours.
In a medium, coverable pot, sauté onion and garlic in olive oil with a pinch of salt and pepper on medium heat for about a minute or two until they become translucent.
Brown the pork or chicken on all sides for 2-3 minutes each.
Add the mushrooms and tomatoes and saute for 5 minutes until the tomatoes begin to wilt.
Add the marinade and butter to the pot.
Cover, raise heat to medium-high and bring to a slow boil. When it comes to a boil, lower heat to medium-low and let simmer for about 3 hours.
Take off heat and let cool for 10 minutes. Then, with two forks, shred the meat so it becomes “pulled.” Serve on bread of your choice.