Preheat the oven to 350℉. Place the brisket, fat side up, in a roasting pan.
In a medium bowl, mix together worcestershire sauce, mango chutney, ketchup and mustard. Pour over the brisket. Sprinkle the chopped onions on top of the brisket. Bake for one hour, uncovered.
Remove from the oven and sprinkle the carrots around the brisket. Cover and bake for an additional 3 hours.
After roasting, cut away the fat with a sharp knife and discard. Slice against the grain and serve.