1 slab (about 3 pounds) center-cut beef brisket
4 slices thick bacon, cut crosswise into 1/4-inch slivers
24 pearl onions, peeled, or 6 small onions, peeled and quartered
8 medium-size carrots, peeled, trimmed, and cut crosswise into 2-inch pieces, plus 2 carrots, peeled, trimmed, and finely chopped
1 pound small red or new potatoes, cut in half
Coarse salt and freshly ground black pepper
1 onion, peeled and finely chopped
2 ribs celery, finely chopped
2 cloves garlic, peeled and finely chopped
2 bay leaves
1/2 cup Cognac
1 bottle (750 milliliters) fruity red wine, like Beaujolais
2 tablespoons tomato paste
1 tablespoon chopped chives (optional)
Preheat the oven to 275 degrees Fahrenheit. Trim any excess fat (more than 1/4 inch) off the brisket.Place the bacon in a large heavy pot or Dutch oven over medium heat and cook until browned, about 3 minutes. Using a slotted spoon, transfer the bacon to a platter.
Add the pearl onions, carrot pieces and potatoes to the pot, increase the heat to medium-high, and cook until browned (about three minutes), stirring often. Using the slotted spoon, transfer the browned onions, carrots and potatoes to the platter with the bacon. Lightly cover the bacon and vegetables with aluminum foil — they won't be added back to the pot until the brisket has cooked for three hours. Pour off and discard all but about two tablespoons of the bacon fat from the pot.
Very generously season the brisket on all sides with salt and pepper. Place the brisket in the pot and sear it in the hot bacon fat over medium-high heat until darkly browned, about five minutes per side. Transfer the brisket to a plate. Pour off and discard all but two tablespoons of fat.
Add extra two chopped carrots, second chopped onion, celery, garlic and bay leaves to the pot and cook until browned, about four minutes, stirring often.
Add the Cognac and let come to a boil, stirring up the brown bits from the bottom of the pot with the wooden spoon. Return the brisket to the pot. Add the wine and tomato paste and bring to a boil.
Cover the pot with a tight-fitting lid and place it in the oven. Cook the brisket until semi-tender, about three hours, checking once or twice to make sure the meat doesn't stick to the pot or scorch on the bottom.
Remove the pot from the oven. Uncover the pot, and using a large spoon, remove and discard any fat floating on the surface. Stir in the bacon, browned pearl onions, carrot pieces, and potatoes. Cover the pot, return it to the oven, and continue cooking the brisket for 1 hour longer.
Remove the pot from the oven. Uncover the pot, spoon off the fat again, and return the uncovered pot to the oven. Cook the brisket until it is very tender, some of the pan juices have evaporated, and the sauce starts to thicken, 30 minutes to one hour more. Remove the pot from the oven and let the brisket rest for about 10 minutes.
Again, spoon off any fat that has risen to the surface. Remove and discard the bay leaves. Transfer the brisket to a cutting board and thinly slice it crosswise across the grain.
Place the pot with the sauce and vegetables on the stove over medium-high heat and bring to a boil. Boil the sauce until concentrated and flavorful, about three minutes. Taste for seasoning, adding salt and pepper to taste; the sauce should be highly seasoned.
Return the sliced brisket to the sauce and vegetables. Sprinkle the chopped chives, if using, on top. Serve the brisket French bistro style directly from the pot.