Thaw pastry according to package directions. Meanwhile, in a large skillet brown steaks, half at a time, in hot oil over medium-high heat for 1 minute on each side. Drain on paper towels. Cool. Stir together pate, crumbs, parsley, basil, garlic salt, and pepper. Spread 1 tablespoon of pate mixture on top of each steak.
On lightly floured surface, roll each sheet of puff pastry into an 11-inch square; cut each into four 51/2-inch squares. Place pastry squares on top of steaks; fold under meat. If necessary, trim pastry so only 1/2 inch remains folded under the meat. Reserve any pastry trimmings. If desired, cut small shapes from pastry trimmings; moisten and place on top of bundles.
Place bundles, pastry side up, on a rack in a shallow baking pan. Bake, uncovered, in a preheated 450 degrees oven 12 to 15 minutes or until pastry is brown and meat is medium-rare (140 degrees ). If necessary, cover loosely with foil during the last 5 minutes to prevent overbrowning. Let stand 10 minutes before serving.
Meanwhile, prepare sauce. In a medium saucepan cook mushrooms and onion in butter or margarine until tender. Stir in cornstarch. Add wine, water, and bouillon granules. Cook and stir until thickened and bubbly, then cook and stir for 2 minutes more. Serve with meat.