Preheat oven to 325°F.
Place a large Dutch oven or sauté pan, lightly coated with olive oil, over medium-high heat. Pat dry the pot roast and season with salt and pepper.
Sear the roast on all sides until the roast is dark brown (about 5 minutes per side). Transfer the roast to a roasting pan.
Add onions to the pan and sauté until deep brown and very fragrant (about 7- 10 minutes).
Add carrots and celery and continue cooking until lightly caramelized.
Add ancho chilies, garlic and prunes and sauté for an additional 2 minutes.
Add tomato paste and cook paste until it has darkened slightly.
Add wine and, using a wooden spoon or spatula, scrape up browned bits.
Transfer all ingredients to roasting pan or keep in a Dutch oven. Add chicken stock.
Cover and braise for 2½ -3 hours or until a fork can easily pierce the meat and will not resist.
Remove meat and lightly tent with foil for 30 minutes.
Strain vegetables out of braising liquid and transfer liquid to a saucepan. Reduce liquid by ⅔ or until it clings to a spoon. Season to taste with salt and pepper.
Remove string from roast and cut into large chunks. Serve with Raisin and Apple Gremolata.