Place blackberries in a bowl. Combine sugar and cornstarch; sprinkle over berries. Add lemon juice and cinnamon; toss to coat. Spoon into a greased 1-quart baking dish.
Roll out pastry; make a lattice crust. Crimp edges. Brush with egg white; sprinkle with remaining sugar.
Bake at 375 degrees for 40-45 minutes or until crust is golden brown and filling is bubbly. Cool on a wire rack.