Preheat oven to 350 degrees.

In a medium bowl, mix melted butter, flour, brown sugar and pecans until well combined. Press into the bottom of a 9x13 inch baking dish. Bake for 15-20 minutes, or until lightly browned; cool completely.

Meanwhile, combine egg whites, sugar, 2 cups of diced berries and lemon juice in a large bowl. Beat with an electric mixer at high speed until whipped and stiff, like meringue.

In a separate bowl, beat the cream and vanilla until stiff peaks form. Fold the whipped cream into the strawberry mixture, Fold in the remaining strawberries.

Spread the mixture over the prepared crust Cover and freeze for at least 6 hours. Let stand at room temperature for about 10 minutes before slicing and serving.