Make pie crusts as directed on box for Two-Crust Pie using 10-inch tart pan with removable bottom or 9-inch glass pie pan. Place 1 pie crust in pan; press in bottom and up sides of pan. Trim edges if necessary.
Place oven rack in lowest rack position; heat oven to 400°F. In medium bowl, mix spinach, ricotta cheese, Parmesan cheese, garlic salt, pepper and egg yolk until well blended; spread evenly in crust-lined pan.
To make lattice top, cut remaining pie crust into 3/4-inch-wide strips; arrange in lattice design over spinach mixture. Trim and seal edges. In small bowl with fork, beat egg white and water; gently brush over lattice.
Bake on lowest oven rack 45 to 50 minutes or until dark golden brown. If necessary, cover torta with foil during last 5 to 10 minutes of baking to prevent excessive browning. Cool 10 minutes; remove sides of pan.