Heat 25g of butter in a frying pan, brown the lamb fillet on all sides and season well, place on to a plate and allow to cool.
In the same pan, melt the remaining 25g of butter. Soften down the shallot for 2-3 minutes, then add the chopped mushrooms. Cook for another 2-3 minutes.
Add the Noily Prat (or Vermouth) and reduce until almost evaporated, add the herbs and season well. Spread on a plate to cool.
Trim pastry to cover lamb with a small overlap. Brush the pastry with egg wash, sprinkle with the chopped herbs. Spread with the mushroom mixture. Place the lamb loin into the centre of the pastry, wrap the pastry around the lamb and seal the ends and the seams.
Place on a baking sheet with seam underneath. Egg wash the pastry and place in the fridge for 30 minutes to rest.
Pre heat oven to 195°C.
Place the shallots, parsley, thyme, stock, sherry and seasoning in a solid steam container and steam for 30 minutes.
Melt the butter for the sauce in a small sauté pan. Cook the chopped shallots for 2-3 minutes until soft. Add the red wine and bubble until reduced by half. Add the sprig of thyme, stock and jam, bubble again until reduced by a quarter.
Pass through a fine sieve and pour into a clean pan. Put to one side.
Putting the dish together
Remove lamb from the refrigerator, if your own has a food probe, put the roast probe into the centre of the lamb and place into the oven.
See the core temperature at 65°C, when the oven switches off, take out the lamb, remove the probe, otherwise place the lamb in the oven and bake for 25-30 minutes and leave to rest for 5-10 minutes – DO NOT COVER.
Heat the butter for garnish and cook small mushrooms for 2-3 minutes.
Heat sauce, adding raspberries, shredded mint and season. Thicken with a little of the arrowroot if needed.
Trim the end of the lamb, and then slice the lamb 3 or 4 pieces.
Place asparagus on a plate, 3 or 4 pieces per portion. Place slices of lamb on asparagus tips. Decorate the plate with the braised shallots and mushrooms. Drizzle with sauce, dot with raspberries and a few radish leaves.