Soak porcini mushrooms in boiling water for 10 minutes, then strain (reserving the soaking liquid).
Heat a little oil in a non-stick frying pan. Season the veal with salt and pepper and fryi in two batches over medium high heat until browned on each side, about 1 minute per side. Remove and keep warm.
In the same pan, brown the fresh mushrooms in a little more oil over high heat. Add the garlic and sherry vinegar to deglaze. Add the porcini, soaking liquid and stock. Simmer about 3 minutes until thick and glossy. Season if necessary and pour over veal to serve.