Heat oven to 350°F. Grease and flour 8-inch square baking pan; set aside.
Combine butter and sugar in bowl. Beat at medium speed, scraping bowl often, until creamy. Add egg whites; continue beating until well mixed. Stir in sour cream and vanilla. Add flour, baking powder, salt and half & half; beat at low speed just until combined.
Pour batter evenly into prepared pan. Bake 30-35 minutes or until toothpick inserted in center comes out clean. Cool completely.
Combine strawberries and cornstarch in 1-quart saucepan. Cook over medium heat, stirring occasionally, 4-5 minutes or until mixture boils and thickens. Cool 15 minutes.
Spoon strawberry mixture onto cake, spreading evenly. Cover; refrigerate at least 2 hours or until chilled. Serve with whipped cream, if desired.
- When fresh strawberries are plentiful, arrange halved or sliced berries on cake before topping with cooked strawberry mixture.
- For a quick topping, use a 21-ounce can strawberry pie filling; spread on top of cake and refrigerate.