Brown veal in butter in a skillet. Transfer veal to a 2-quart casserole; reserve drippings.
Combine water and drippings in top of a double boiler; mix well. Add flour, salt, and paprika; mix until smooth. Cook 1 minute, stirring constantly, until thickened and bubbly.
Remove from heat; gradually add sour cream, mushrooms, and onion juice, mixing well. Pour over veal; cover and bake at 300° for 1 hour. Serve over noodles.