Preheat oven to 80 degrees C.
Clean the fillet and put it in an aluminum foil envelope for baking. Add thyme, butter and unpeeled cloves of garlic, a pinch of salt and pepper. Seal the bag, place over the baking pan and bake for 40 minutes. When the chicken is ready, remove from the bag, slice and leave to cool a little. Save the liquid.
Putparsnip and leek in skillet and add water to just to cover. Bring to a boil, partially cover and let it simmer until the parsnips are soft. Drain the vegetables and save the liquid. Add the vegetables to the liquid from the bag with chicken and toss. Add the broth of the parsnips if necessary. Season with salt and pepper.
Place the puree on the bottom of the serving plate and arrangethe chicken slicesand top with parsnip. You can garnish with sprouts and thinly sliced peppers.