Put the cottage cheese through a sieve and let liquid drain out. You should get between ⅓ and ½ cup of liquid, but don't be too concerned about how much drains out. Brands seem to vary. Save the liquid for another use and puree the cottage cheese in a food processor. Keep the processor handy for making graham cracker crumbs and whipping the cream.
Mix gelatin (I prefer 4 teaspoons, but the original recipe says 2 packets or 5 teaspoons), 1 cup sugar, and ⅛ scant teaspoon salt in the top of a double boiler, off heat.
Whisk together 2 egg yolks and cold milk, then whisk into the gelatin mixture. Set over boiling water, stirring constantly until gelatin is dissolved and mixture thickens just slightly. About 10 minutes.
Remove from heat, add the lemon zest, and let cool.
Pour gelatin mixture into a bowl and stir in the pureed cottage cheese, lemon juice, and vanilla. Chill, stirring occasionally until mixture mounds slightly when dropped from a spoon (this should about an hour).
While mixture is chilling, make crumb topping (as written below) if you plan on using it.
When gelatin mixture has thickened slightly and forms mounds when spooned, beat the egg whites until stiff peaks form and fold them into the gelatin mixture. Fold in the whipped cream.
Turn into an 8 or 9-inch spring form pan and sprinkle top with crumb mixture. Chill until firm (6 to 8 hours).