In a bowl, mix the brown sugar, salt, garlic powder, cayenne pepper, paprika, black pepper, cinnamon, cocoa, coriander, and white pepper. Rub the mixture all over the brisket, set in a baking dish, and cover with foil. Refrigerate overnight.

Preheat the oven to 350°F. In a large, enamelled, cast-iron casserole, heat the oil over medium-high heat on the stovetop. Add the brisket, fat side down, and brown for 6 minutes per side. Transfer to a plate.

Reduce heat to medium and add onions. Stir well. Cover and cook, stirring occasionally, until softened, about 15 minutes. Add the carrots, cover, and cook, stirring occasionally until the carrots begin to soften, about 3 minutes. Transfer everything to a bowl.

Add tomatoes and Organic Mostarda Chiantigiana di Peperoni to the casserole and stir over medium heat. Add the brisket and any juices, and spread the onions and carrots around the meat. If necessary, add enough water to half-submerge the brisket in liquid. Cover tightly and braise in the oven for 2 1/2 hours.

Transfer the brisket to a cutting board, cover with foil, and let stand for 30 minutes. Raise the oven temperature to 425°F/220°C. Slice the meat across the grain 1/4 inch thick, return to the casserole, and spoon the sauce over the meat.

Return the casserole to the oven and cook uncovered for 1 hour, or until the meat is fork-tender. Check every 20 minutes, and if necessary, add water.