Place meat in clear plastic bag; set in deep bowl.
Combine Burgundy, dry sherry, bay leaves, and onion.
Pour over meat in bag; close.
Chill overnight; turn bag occasionally to dis- tribute the marinade.
Next day, remove meat from bag; reserve marinade.
Place meat on rack in shallow roasting pan.
Insert meat ther- mometer.
Roast at 425° till thermometer registers 130°, about 55 minutes.
Remove meat from pan; cool 20 minutes.
Reserve drippings.
Trim any fat from meat.
Meanwhile, cook mushrooms and leek in butter till tender, about 6 minutes.
Remove from heat; stir in pate, crumbs, and 3 tablespoons of the reserved marinade.
(Save remaining marinade) Cover; chill at least 1 hour.
Stir together the 2 cups flour and 1/2 teaspoon salt.
Cut in shortening till size of small peas.
Gradually add 1/3 to 1/2 cup cold water, 1 tablespoon at a time, tossing with fork till all is moistened.
Form into a ball.
On floured surface roll dough to a 14x12-inch rectangle.
Spread mushroom mixture to within 1 inch of edges.
Center meat atop.
Overlap long sides.
Brush edges with egg; seal.
Trim excess pastry from ends; fold up.
Brush with egg; seal.
Place roast, seam down, on greased baking sheet.
Brush egg over all.
Reroll pastry trimmings.
Cut into strips; criss cross on roast.
Brush with remaining egg.
Bake at 425° till pastry is golden, 30 to 35 minutes (meat will be rare).
Heat cup water with reserved drippings till solids dissolve.
Mix 1/2 cup cold water with 3 tablespoons flour; stir into drippings with 14 cup reserved marinade.
Cook and stir till bubbly; season with salt and pepper.
Serve with roast.