For sauce: Heat the butter in a heavy-based saucepan.
Add the onion and garlic and sauté until onion is translucent.
Add the mushrooms and sherry and flambé.
Add the mustard and mix through.
Gradually add the cream and chicken stock.
Cook uncovered until sauce starts to thicken.
Stir in the thyme.
Cook the gnocchi according to instructions on pack.
Drain and keep warm.
Heat the ghee in a heavy-based frying pan.
Add the meat and fry until golden brown.
Squeeze a little lemon juice over meat whilst cooking.
Remove from pan and season to taste.
Divide the gnocchi between 4 plates.
Spoon meat in the centre of each plate and spoon mushroom sauce over.
Garnish with fresh thyme and serve immediately with pecorino shavings.