Cover the beef with red wine and marinate for 24 hours.
Preheat the oven to 400°F. Transfer the beef to a baking sheet, reserving the marinade. Season with salt and pepper and roast for 25 minutes, until browned, stirring halfway through.
Reduce the oven to 300°F.
For the sauce, heat a large skillet over medium heat. Add the bacon and cook until the fat is rendered and the meat is crisp. Add the carrots, onion and celery, cooking until softened, about 5 minutes. Add the flour and stir until all fat is absorbed. Cook over low heat for 10 minutes, stirring regularly.
Add the tomato paste and reserved marinade. Bring to a boil. Add the beef bouillon and 2 cups of water and return to a boil. Cook until reduced and flavorful.
When the beef is finished browning, place it in a braising dish with a lid. Add the sauce. Cover the pan with a piece of parchment paper, then a piece of aluminum foil, then the pot lid to ensure no steam escapes. Braise at 300°F for 1-2 hours, until the beef is very tender.
Chill slightly to skim any fat off the surface of the sauce. Cover to keep warm.
Increase the oven to 450°F.
On a baking sheet, toss the carrots, rutabaga, celeriac, parsnips, sage, oil, salt and pepper. Roast for 20-25 minutes, until caramelized. Cool slightly, then sprinkle with parsley.
In a large stockpot, place the potatoes and a generous pinch of salt. Cover with cold water and bring to a simmer. Cook at a simmer until the potatoes are fork-tender, about 15 minutes. Drain the potatoes and return to the pot. Add the butter, milk, buttermilk, salt and pepper. Mash until smooth. Fold in the scallions.
On a baking sheet, toss the mushrooms with the garlic, oil, salt and pepper. Roast for 15 minutes, until tender.
To serve, divide the mashed potatoes and beef stew between plates. Add roasted mushrooms and vegetables o on the side.