Beef Wellington

My new favorite!  I'm already planning to ask for this on my birthday.
4 beef tenderloin steaks (6 oz each)
3/4 tsp salt, divided
1/2 tsp pepper, divided
2 Tbl olive oil, divided
1 1/4 cups sliced fresh mushrooms
1 medium onion, chopped
1 pkg frozen puff pastry, thawed
1 egg, beaten

1. Sprinkle steaks lightly with 1/2 tsp salt (I used Sea Salt) and 1/4 tsp pepper.  In a large, very hot skillet, brown the steaks in 1 Tbl oil for 2-3 minutes on each side.  Remove from skillet and refrigerate until chilled.
2. In the same skillet, now at medium heat, saute the mushrooms and onion in remaining onion until tender.  Stir in remaining salt and pepper and cool to room temperature.
3. On a lightly floured surface, roll each puff pastry sheet into a 14-in. by 9 1/2 in. squares (use scraps to make decorative cutouts if desired).  Place a steak in the center of each  square; top with mushroom mixture.  Lightly brush pastry edges with water.  Bring opposite corners of pastry over steak; pinch seams to seal tightly.
4. Place on a greased 15-in. by 10-in. x 1-in. baking pan.  Cut four small slits in top of pastry.  Arrange cutouts over top if desired.  Brush with egg.
5. Bake at 425 degrees for 25 to 30 minutes or until pastry is golden brown and meat reaches desired doneness (for medium-rare, a meat thermometer should read 145 degrees, medium 160 degrees, well-done, 170 degrees).