In medium saucepan melt butter.
Stir in flour, walnuts, and brown sugar.
Spread evenly in 13x9x2-inch baking pan.
Bake in 350° oven for 20 minutes or till lightly browned, stirring occasionally.
Remove 1/3 of the crumbs; set aside.
Spread remaining crumbs evenly in pan.
In large mixer bowl combine egg whites, strawberries, granulated sugar, and lemon juice.
Beat at low speed of electric mixer about 2 minutes or till mixture begins to thicken.
Beat at high speed for 10 to 12 minutes or till stiff peaks form.
Whip cream just till soft peaks form; fold into strawberry mixture.
Or, fold thawed dessert topping into strawberry mixture.
Spread over crumbs in pan; top with remaining crumbs.
Cover and freeze for 6 hours or overnight.