Soften:

1 env. unflavored gelatin in 1/4 c. cold water

Mix in saucepan:

3 egg yolks, slightly beaten
1/2 c. sugar
1 tsp. vanilla
1/4 tsp. salt
1 c. milk

Cook until custard thickens, add softened gelatin and cool completely. Beat 3 egg whites, stiff. Add:

1 c. cream, whipped stiff or
2 to 3 c. whipped topping and cooked custard mixture

Blend on low speed with mixer. Roll or crush enough chocolate Hydrox cookies to cover bottom of a 9 x 13 pan. Put custard mixture on top of cookie crumbs and top with some remaining crumbs. Chill.