General tips
Use a real bottle of Burgundy or Beaujolais, not cooking wine. The wine is the soul of this dish - if it tastes bad on its own, it'll taste worse after reducing. A $12 Pinot Noir is the right floor for ingredient quality. Cook the rest with dinner.
Brown the chicken AND the lardons before bagging. Both contribute layers of flavor that no amount of sous vide time can create. Render the bacon first, set it aside, then brown the chicken in the bacon fat. That's the foundation.
Sous vide at 155°–160°F for 4–6 h. Lower and the dark meat doesn't fully render; higher and the white meat (if you're using a whole bird's worth of pieces) dries out. Six hours is the sweet spot for legs and thighs.
Reduce the marinade-wine mixture in a separate pan while the chicken cooks. Pour off the bag liquid, reduce it by half with the leftover marinade, and finish with a knob of butter and a dash of brandy. That's your sauce - concentrated, glossy, deeply winey.
Anti-tip: don't add the pearl onions and mushrooms to the sous vide bag. They turn to mush at 155°F and bleed their water into the sauce. Sauté them separately in butter until golden, then fold them into the finished dish.
Tender tips
Sear the skin after sous vide for crispy texture
Use a good-quality red wine you'd drink - it affects the flavor
Make the sauce while the chicken cooks for efficiency
Very Tender tips
This temperature is ideal for older, tougher birds
The meat will be fall-off-the-bone tender
Great for making ahead - texture holds well when reheated