Take a few dried Porcini mushrooms, crumple until about 1Tblspn then soak in a cup of boiling water Cut six medallions, 4cm thick, out of a pork tenderloin. In a hot skillet sear each face in butter to colour. Place in a hot oven, 200C, for about ten minutes, reserve.
Meanwhile trim, removing the coarse stalks, of 1/2lb chestnut mushroom into thick slices together with a box of mixed wild mushrooms. Keep the trimmings add to the porcini then bring the trimmings to a simmer, adding the juices from the reserved medallions. In the same skillet add more butter and fry off at a medium heat all the mushroom slices until they lose water, colour slightly and become soft. Reserve.
Finely dice a large white onion and sweat off in the skillet with more butter if necessary, raise temperature drive of the liquid until the fat runs then strain the trimmings stock over the onions. Leave to simmer until the stock has fully reduced.
Make a thick white sauce, blending 1.5 Tblspn into 2oz butter then stir adding about 1/2pint of milk, keep stirring until the sauce is thick and smooth. Combine with the reserved onions and then add 2Tblspn of double cream and the last minute, final stir to fully combine.
In an oven proof dish just large enough to take the medallions with room to spare, sprinkle the base with two sprigs of finely chopped sage and a crushed garlic. Space the medallions the scoop the mushrooms into the spare spaces and push them into all the gaps.
Finally cover the mushrooms and medallions with the white sauce.
Enjoy