Cut the wild boar shoulder into even cubes. In a large bowl, combine the marinade ingredients: Côtes de Gascogne red wine, wine vinegar, bouquet garni, chopped leek, garlic, studded onions, salt, and pepper. Add the meat, mix thoroughly, cover, and refrigerate for 48 hours, stirring occasionally. This step ensures tender, deeply flavored results drawn from traditional French game cooking techniques.
Drain the meat and strain the marinade, reserving both. Peel and quarter the shallots. In a large casserole over medium heat, melt a little duck fat and sear the boar pieces on all sides until golden. Sprinkle with flour, stir briefly to lightly brown, then deglaze with the strained marinade diluted with 50 cl water. Add diced carrots and celery, baby onions, quartered shallots, and lardons. Season, cover, and simmer gently for 1h30, checking liquid levels and adding water if needed.
Remove the meat to keep warm. Strain the cooking juices, return to the casserole, and reduce until thickened to your liking. Return the meat and add button mushrooms; simmer 10 minutes over low heat to meld flavors.
Serve the stew piping hot in a deep dish, sprinkled with chopped flat-leaf parsley. Garnish with croutons toasted in duck fat for authentic crunch.
Suggested side: pumpkin blinis
