Marinate the Beef
In a large glass bowl, combine the beef chunks, carrots, celery, shallots, leeks, thyme, bay leaf, garlic, peppercorns, and parsley stems. Pour the entire bottle of wine over everything until the beef is submerged. Cover and refrigerate for 12 hours (or overnight), stirring a couple of times for even marinating.

Prepare the Beef for Searing
About 30 minutes before cooking, remove the bowl from the refrigerator. Remove the beef pieces and pat them completely dry with paper towels—this is crucial for a good sear. Season generously with salt and pepper on all sides and let sit at room temperature. Reserve the wine marinade with all the vegetables and herbs.

Cook Down the Marinade
Pour the reserved wine marinade into a medium pot. Bring to a boil, then reduce to a gentle simmer. Cook for about 20 minutes until reduced by one-third, skimming off any foam that rises to the surface. Strain the wine through a fine-mesh sieve, discarding the vegetables and herbs. Set the strained wine aside.

Sear the Beef
Heat 2-3 tablespoons of olive oil in a heavy Dutch oven over high heat. Working in batches, add the beef pieces in a single layer—don't crowd the pan. Sear for about 2 minutes per side until deeply browned. If browning too quickly, lower the heat to medium-high. Transfer to a plate and repeat with remaining beef, adding more oil as needed between batches.

Braise the Beef
In the same Dutch oven, add more oil if needed. Add the tomato paste and cook for about 1 minute, stirring constantly, until fragrant and darkened. Add the minced garlic and cook for 30 seconds. Return all the seared beef to the pot. Pour in the strained wine and beef broth. Add the rosemary sprigs, sliced leek, diced fennel, and bay leaf. Bring to a boil, then reduce the heat to low. Cover and simmer for 2½ to 3 hours, until the beef is fork-tender.

Cook the Pearl Onions
While the beef braises, prepare the vegetables. In a large skillet over medium heat, add the diced pancetta (or bacon/pork belly) and cook until crispy and browned, about 5-7 minutes. Remove the pancetta and set it aside, leaving the fat in the pan. Add the pearl onions and cook, stirring occasionally, until golden brown, about 8-10 minutes. Season with salt and pepper. Remove and set aside with the pancetta.

Cook the Mushrooms
Using the same skillet, add 1 tablespoon of butter if needed. Add the mushrooms in a single layer, season with salt, and spread evenly. Let them cook undisturbed for 3-4 minutes to develop a golden crust, then stir and sauté for another 3-4 minutes until browned and any liquid has evaporated. Remove and set aside with the onions and pancetta.

Cook the Carrots
In the same skillet, add another tablespoon of butter. Add the carrot pieces and cook for about 4 minutes, stirring occasionally, until just starting to soften but still have a bite. Season with salt and pepper. Remove and add to the onions, mushrooms, and pancetta.

Add the Vegetables to the Stew
Once the beef is fork-tender, remove and discard the rosemary sprigs, thyme sprigs, leek, fennel, and bay leaf. Add all the cooked vegetables—pearl onions, carrots, mushrooms, and pancetta—to the pot. Stir gently and cook uncovered over medium-high heat for about 5 minutes, stirring occasionally, until the carrots are tender and everything is heated through.

Make the Roux and Finish the Dish
In a small saucepan, melt the butter over medium heat. Whisk in the flour and cook, stirring constantly, for 2-3 minutes until smooth and lightly golden. Add the roux to the stew, stirring gently. Lower the heat to medium-low and cook for 5-10 minutes, stirring occasionally, until the sauce thickens to a velvety consistency.

Taste and adjust
Taste and adjust seasoning with salt and pepper. Squeeze fresh lemon juice over the top and garnish with fresh parsley. Serve over mashed potatoes, roasted potatoes, buttered pasta, or creamy polenta. Enjoy!