In a mixing bowl, stir together flour, salt, and basil. Cut in shortening with a pastry blender until pieces are pea size. Sprinkle 1 tablespoon water over part of the mixture; gently toss with fork. Push moistened dough to side of bowl. Repeat with remaining water, until entire mixture is moistened. Divide in half; form each half into a ball. Cover and set aside.
Remove casing from sausage, if present. In a large skillet, cook sausage, ground beef, onion, mushrooms, and garlic until meat is brown and onion is tender. Drain well. Stir in tomato sauce, Parmesan cheese, and Italian seasoning. Cook and stir until heated through. Cover and keep warm.
On a lightly floured surface, roll half of the pastry into a 13-inch circle. Place pastry in a 9-inch springform pan so dough extends about 2 inches up the sides. Sprinkle bottom with half of the mozzarella cheese. Spoon meat mixture over cheese.
Pat spinach dry with paper towels. Combine spinach, roasted sweet peppers, whole egg, and remaining mozzarella cheese. Spread mixture over meat mixture.
Roll remaining pastry into a 10-inch circle; cut into 3/4-inch-wide strips. Twist strips and place on spinach mixture to form a lattice. Fold edge of bottom pastry over lattice ends; crimp to seal. Brush pastry with mixture of egg yolk and water; sprinkle with sesame seed.
Bake in a 375 degree F oven for 45 minutes or until golden brown. Cool 10 minutes on a wire rack. To transport, cover with foil and place in an insulated container. To serve, remove sides of springform pan; cut tart into wedges. Serve within 3 hours. Makes 10 servings.