Make incisions in the chicken breast fillet and brown on both sides. Sprinkle with sea salt, vacuum seal with a tablespoon of goose fat and fresh thyme stems. Cook for 1 hour at 52°C, then cool in ice bath. Before serving, fry the fillet on both sides again.
Caramelise brown sugar in a sauce pan, add wine vinegar and forest fruit. Cook for 5 minutes on low heat, then set aside to strain for 2 hours. Mix the forest fruit juice with the demi-glace obtained in this way, and set aside remaining sauce to thicken.
Trim the parsnips on both sides and chop into cubes. Cook in milk seasoned with a bay leaf, together with carrots and sliced leek. Boil the remaining pieces of parsnips, purée, mix, add burned butter and strain carefully.
Plate the chicken fillet, pour fruit sauce over it, place cooked vegetables on top, spoon parsnip purée in mounds around the meat.