Heat oven to 275°F. Line cookie sheet with cooking parchment paper. In large bowl, beat egg whites and cream of tartar with electric mixer on medium speed until foamy. On high speed, beat in 1 tablespoon of the granulated sugar at a time until stiff glossy peaks form and sugar is almost dissolved, about 6 minutes. Spread meringue to form 10x10-inch heart shape on cookie sheet, building up edges with back of spoon.
Bake 45 to 50 minutes or until firm and dry to the touch. Turn oven off; let meringue shell stand in closed oven 1 hour. Slide meringue shell and parchment paper from cookie sheet onto wire rack. Cool completely, about 10 minutes.
Meanwhile, in medium bowl, beat whipping cream with electric mixer on high speed until stiff peaks form. In large bowl, beat cream cheese and powdered sugar with mixer on medium speed until fluffy. Gradually beat in melted baking bar until smooth and creamy. Gently fold in whipped cream.
Carefully remove meringue shell from parchment paper; place shell on serving plate. Spread cream mixture evenly in shell. Cover; refrigerate at least 2 hours.
In medium bowl, gently mix pie filling and strawberries. Spoon 1 1/2 cups fruit mixture over top of dessert. Garnish with mint sprigs. Serve remaining fruit mixture to be spooned over individual servings.