Combine flour, nuts, brown sugar, and melted margarine.
Mix well and spread into 13x9-inch pan.
Bake at 350 degrees for about 20 to 25 minutes, stirring to crumble.
Combine egg whites, sugar, strawberries, and lemon juice in a large deep mixing bowl.
Beat with electric mixer at high speed for 15 minutes.
Fold in whipped cream or whipped topping.
Place one-half the crumbs in bottom of the pan.
Pour in strawberry mixture, then top with remaining crumbs.
Freeze until firm.
Cut into squares to serve.
Top each serving with whipped topping, if desired.
This is really a "Supreme" dessert.