Sauté the veal in a little (extra) butter briefly until browned, season with salt and pepper, and drain on paper towels. Don't overcook the meat - it should just be browned on the surface at this point since it will cook more in the sauce.
Add butter to the pan you sautéed the meat in, and cook the onion until transparent. Add the mushrooms and sauté. Add the flour. Add a pinch of dried thyme (optional).
Add the wine and cook down rapidly over high heat. Add the meat back. (If the wine is too mellow, add a little lemon juice).
Dissolve the cornflour in the cream, and add this to the pan, stir and let bubble just until the meat is cooked but still tender.
Take off the heat and adjust the seasoning. Serve with plain rice, buttered rice, boiled potatoes, pasta, or (most traditionally) with rösti or knöpfli (spaezle).