Partially thaw frozen fruits; do not drain.
Stir together the 3-1/4 cups flour and salt in a large mixing bowl. Cut in shortening until size of small peas.
Place egg yolk in a 1-cup measure. Add enough milk to make 1/2 cup. Beat with a fork until combined. Add milk mixture to flour mixture 1 tablespoon at a time, tossing lightly with a fork until all is moistened. Divide dough in half; form each half into a ball.
Roll one portion of dough on a lightly floured surface into a 17x12-inch rectangle. Wrap the pastry around rolling pin. Unroll onto an ungreased 15x10x1-inch baking pan. Gently ease pastry into pan. Trim pastry even with sides of pan. Sprinkle cornflakes over pastry.
Stir together the 1 cup sugar, the 1/4 cup flour, and cinnamon in a very large mixing bowl. Add fruit; toss to coat. Sprinkle fruit over cornflakes.
Roll out remaining dough into a 17x12-inch rectangle. Arrange over fruit. Trim pastry to 1/2 inch beyond sides of pan. Seal top pastry to bottom pastry; crimp edges. Cut slits in top pastry.
Brush egg white over top of pastry; sprinkle with sugar. Bake in a 375 degree F oven about 45 minutes or until golden brown. Cool on a wire rack. Cut into bars. Makes 36.