Stir together the flour, brown sugar, walnuts, and melted butter in a bowl. Spread out on a baking sheet, and bake in preheated oven for 20 minutes until crispy, then remove from oven and allow to cool completely.
Beat the egg whites to soft peaks; continue beating to stiff peaks while slowly adding sugar. Toss the strawberries in lemon juice, and stir into the egg whites until the mixture turns slightly pink. Fold in the whipped cream until incorporated.
Crumble up the walnut mixture, and sprinkle 2/3 of it evenly on the bottom of a 9x13 inch dish. Spoon the strawberry mixture over the crumbs, then sprinkle the remaining crumbs over top. Place in freezer and freeze for two hours until hard. Remove from the freezer several minutes before serving to make it easier to slice.
