if you get a whole chicken and take the breast and the legs aside for a main-dish
you'll have the "carcasse"
add cold water in a pot, add the carcasse of the chicken, and some cellery, ognions, karotts and poree cut in small pieces (not in cubes, just in pieces). bring it to sear, and hold it there for 30 minutes.
let it rest until it has room temperature.
(as always a stock is not salted ! the osmosis acts for you if you don't
add butter and flour in a pot, and bring it to melt and combine, add the room-cold stock and bring it while stirring to boil up. let it simmering for 30 minutes, add salt and a hint of nutmeg (also good just a hint anis),
add fresh cream as liked
dry-roast the boletus and add salt, pepper and a hint cognac, add a scoop of the soup, and let it reduce.
take a filo-dough (also foil for springroll do work) and place it in the center, form a bag, and close it using a stipe porre or similar.
put it into the oven at 220°c for 15 minutes.
in a soupe-plate add some soupe, but the mushroom-bag in the center and if you like drop some drops of a good truffle-oil on top of the soup.
the boletus can be substitute with wild Xerocomus badius (in this case do not leve them to long in the sauce "reducing" because they thend to get to soft)