Crush graham crackers into fine crumbs; then add margarine and stir to mix.
Line bottom and sides of a 9 in. (23 cm) spring-form pan with the crumb mixture.
Chill.
Sprinkle gelatin over cold water and allow to soften for several minutes.
Beat egg yolks slightly; then pour into nonstick saucepan or top of double boiler.
Stir in fructose, sugar replacement, salt, and milk.
Cook and stir over medium heat until mixture is thick and coats a spoon.
Cool.
Stir in cottage cheese and vanilla extract.
Beat cottage cheese mixture until light and fluffy.
Beat egg whites until stiff.
Fold egg whites into cottage cheese mixture.
Fold nondairy whipped topping into cottage cheese mixture.
Transfer to a graham crust.
Freeze for 8 to 10 hours or overnight.