1. Put the meat in a pot filled with water, along with the bouquet garni, a handful of coarse salt, and 10 peppercorns.
Cook for 2 hours and 30 minutes over medium heat, covered, skimming the surface regularly.
Peel the shallots, slice them thinly, and melt them in 20 grams of butter for 10 minutes.
Add the sugar and vinegar, let it caramelize for a few minutes over low heat.
Drain the meat, shred it, and mix it with the shallots.
Spread the meat in a gratin dish.
Cover with mashed potatoes, sprinkle with breadcrumbs, and pour the remaining melted butter on top.
Bake in a preheated oven at 425°F for 20 minutes.