To prepare bottom layer, weigh or lightly spoon flour into a measuring cup; level with a knife. Combine flour and salt; stir with a whisk. Combine granulated sugar, egg substitute, ¼ cup melted butter, 2 tablespoons water, vanilla, eggs, and chocolate syrup in a medium bowl; stir until smooth. Add flour mixture to chocolate mixture, stirring until blended. Pour batter into a 13 x 9 inch metal baking pan coated with cooking spray. Bake at 350° for 23 minutes or until a wooden pick inserted in center comes out almost clean. Cool completely in pan on a wire rack.