You’ll begin by patting the chuck roast dry with paper towels. Next, you’ll season the roast with salt and pepper and dredge it in flour, shaking off any excess. Heat the olive oil in a large Dutch oven and sear the roast on all sides until nicely browned, then transfer the roast to a plate to rest. Add more olive oil to the pan along with the carrots, onions, celery, leeks, garlic, salt, and pepper, and cook until the vegetables are tender, but not browned. Add the wine and Cognac and bring to a boil, then add the tomatoes, chicken stock, bouillon cube, and more salt and pepper. Tie sprigs of rosemary and thyme together with string, then add those to the pan, too.
You’ll then add the roast back to the Dutch oven and bring the liquid to a boil. Place the lid on, and braise for 2 1/2 hours at 325°F. Reduce the heat to 250°F and continue to braise for one more hour. Remove the roast from the pan, discard the herbs, and add half the sauce and vegetables to a blender or food processor and puree until smooth. Transfer the puree to a pot and bring to a simmer. Mix together flour and butter in a small bowl, then add the mixture to the puree and simmer until thickened. Serve the roast with the sauce poured over it.