Preheat oven to 350 degrees F. Line an 8 inch square metal pan with nonstick foil.
With an electric mixer, beat butter, 1/4 cup of the sugar, egg yolks (reserve whites) and 1/2 teaspoon of the vanilla and salt. Stir in flour and cornstarch. If necessary, use your hands to mix all ingredients, but do not over beat. Press into bottom of lined pan and bake for 18 minutes or until lightly brown around edges.
Remove from oven and let cool for about 10 minutes. Spread cold (this helps keep the chocolate morsels from melting too much) raspberry pie filling or preserves over crust. Sprinkle chocolate morsels over raspberry filling.
In a large bowl, beat egg whites until soft peaks form, then gradually add remaining 1/2 cup sugar, beating until peaks are stiff. Beat in vanilla.
Spread the egg white mixture over raspberries and chocolate. Return to oven and bake for about 22-25 minutes. Let cool for 15 minutes. Using parchment as handle, lift from pan. Cut into 12 squares.