1 1/4 cups zwieback toast crumbs
2 tablespoons granulated sugar
1/3 cup margarine, melted
1 envelope unflavored gelatine
1/4 cup cold water
1/4 cup lime juice
3 eggs, separated
1/2 cup granulated sugar, divided
1 1/2 teaspoons grated lime peel
16 ounces Neufch?el cheese, softened
Few drops green food coloring (optional)
2 cup thawed frozen whipped topping

Combine crumbs, sugar and margarine; press onto bottom of 9-inch springform pan. Bake at 325 degrees F for 10 minutes. Cool.

Soften gelatine in water; stir over low heat until dissolved. Add juice, egg yolks, 1/4 cup sugar and peel; cook, stirring constantly, over medium heat for 5 minutes. Cool.

Gradually add gelatine mixture to Neufch?el cheese, mixing at medium speed of electric mixer until well blended. Stir in food coloring.

Beat egg whites until foamy. Gradually add remaining sugar, beating until stiff peaks form. Fold egg whites and whipped topping into Neufch?el cheese mixture; pour over crust. Chill until firm. Garnish with additional lime peel, if desired.