Season the saddle of lamb. Brown it in olive oil in a roasting pan in a preheated 160°C oven for 20 to 25 minutes - the meat should remain pink in the centre. Let rest in a warmplace.
Brown the lamb bones and trimmings in a little olive oil in a saucepan. Then add the finely chopped shallots, the clove of garlic (unpeeled and crushed), the sliced mushrooms, the thyme and bay leaves. Deglaze with the soysauce.
Cover with the chicken stock and let reduce slowly, skimming the surface regularly, until a good consistency is achieved. Strain, correct the seasoning with salt and pepper and thicken as desired by whisking in some butter or olive oil.
Slice the meat. Place the slices of lamb on plates, garnish with the sauce and a bouquet of vegetables of your choice.