Prep Ingredients: Ensure beef cubes are thoroughly patted dry with paper towels; this is crucial for achieving a good sear. Prepare all vegetables and aromatics as described in the ingredients list. Have liquids measured and herbs ready. Preheat oven to 325°F (160°C) with a rack positioned in the lower third.

Cook Bacon: Place the diced bacon in the cold Dutch oven. Cook over medium heat, stirring occasionally, until the bacon is crisp and the fat has rendered, about 8-10 minutes. Using a slotted spoon, transfer the crispy bacon to a paper towel-lined plate, leaving the rendered fat in the Dutch oven.

Sear Beef: Increase the heat under the Dutch oven to medium-high. Season the dried beef cubes generously with 1.5 teaspoons of the kosher salt and 0.5 teaspoon of the black pepper. Carefully add about half of the beef to the hot fat in a single layer, ensuring not to overcrowd the pan. Sear the beef, without moving the pieces for several minutes per side, until a deep brown crust forms on at least two sides, about 5-7 minutes total per batch. Add olive oil if the pot becomes dry. Transfer the seared beef to the plate with the bacon. Repeat with the remaining beef, adding more oil if necessary.

Sauté Aromatics: Reduce the heat to medium. Add the chopped onions, carrots, and celery to the pot. Cook, stirring occasionally with a wooden spoon, until the vegetables soften and the onions are translucent and lightly golden, about 6-8 minutes. Add the minced or smashed garlic and cook, stirring constantly, until fragrant, about 1 minute.

Add Tomato Paste & Flour: Stir in the tomato paste and cook, stirring constantly, for 1-2 minutes, allowing it to darken slightly and coat the vegetables. Sprinkle the flour over the vegetables and stir constantly for another 1-2 minutes to cook out the raw flour taste.

Deglaze & Add Liquids: Pour in the red wine (Optional: Add Cognac/brandy first, let it bubble for a minute before adding wine). Increase the heat to medium-high and bring the wine to a simmer. Scrape the bottom of the pot vigorously with the wooden spoon to dislodge any browned bits (fond) stuck to the bottom. Let the wine simmer and reduce by about one-third, about 3-5 minutes. Stir in the beef broth, thyme sprigs, and bay leaves. Add the remaining 0.5 teaspoon salt and 0.5 teaspoon pepper. (Optional: Stir in Worcestershire, soy/fish sauce, or rehydrated porcini liquid now).

Braise Beef: Return the seared beef and reserved bacon (and any accumulated juices) to the pot. The liquid should come about halfway up the sides of the meat or just barely cover it; add a bit more broth if needed, but avoid drowning the meat. Bring the mixture back to a gentle simmer on the stovetop. Cover the pot tightly with the lid and carefully transfer it to the preheated 325°F (160°C) oven. Braise for 2 hours.

Cook Mushrooms & Pearl Onions: About 30 minutes before the initial 2-hour braise is complete, prepare the mushrooms and onions. Heat the butter and 1 tablespoon olive oil in the large skillet over medium-high heat until the butter is melted and foaming. Add the mushrooms in a single layer (work in batches if necessary to avoid crowding). Cook undisturbed for 3-5 minutes, until deeply browned on the first side. Stir and continue cooking, stirring occasionally, until browned all over and any liquid released has evaporated, about 5-10 minutes total. Season the mushrooms with salt and pepper after they have browned. Add the thawed pearl onions to the skillet and cook, stirring occasionally, until lightly browned and heated through, about 5 minutes. Remove the skillet from the heat and set aside.

Add Vegetables & Finish Braising: After the beef has braised for 2 hours, carefully remove the Dutch oven from the oven. Check the beef for tenderness; it should be starting to yield easily to a fork. Stir in the cooked mushrooms and pearl onions. If using potatoes, add them to the pot now. Ensure the vegetables are mostly submerged in the liquid. Return the pot to the oven without the lid (or with the lid slightly ajar) to allow the sauce to reduce and thicken. Continue to braise for another 45 to 60 minutes, or until the beef is completely fork-tender and shreds easily, and the potatoes (if using) are cooked through.

Finish & Serve: Carefully remove the Dutch oven from the oven. Tilt the pot and use a large spoon to skim off any excess fat that has risen to the surface. Fish out and discard the bay leaves and thyme sprigs. If using frozen peas, stir them in now; the residual heat will cook them quickly. Taste the sauce and adjust seasoning with additional salt and pepper if needed. Let the stew rest, uncovered, for 10-15 minutes before serving; this allows the flavors to meld and the meat to relax. Ladle the stew into warm bowls, garnish generously with chopped fresh parsley or chives, and serve immediately.