Stir flour, butter or margarine, brown sugar, and pecans until crumbly. Put into a 9-x-13-inch pan. Bake at 350 degrees until brown, stirring after 10 minutes. Let cool and reserve 1/2 cup for topping.
Beat egg whites until stiff, then slowly add sugar, vanilla, lemon juice, strawberries, and cream or whipped topping. Pour filling over crust, sprinkle reserved crust over filling, and freeze.