Clean the mushrooms and cut into slices. Clean and wash the leek and cut into fine rings.
Cut the meat into finger-thick strips and fry in hot oil until golden brown. Add the leek and mushrooms and fry. Deglaze with cream and stock, bring to the boil and simmer for about 10 minutes over low heat.
Season the ragout with mustard, salt, pepper and curry and thicken with a sauce thickener.