Beat egg yolks, milk, lime juice and lime peel in heavy medium saucepan until blended.

Cook over low heat, stirring constantly but gently, until mixture is just thick enough to coat a metal spoon with a thin film and temperature reaches 160°F, about 15 minutes.

Do not allow to boil.

Remove from heat immediately.

Cool quickly: Set pan in larger pan of ice water; stir occasionally and gently for a few minutes to hasten cooling.

Press piece of plastic wrap onto surface of custard to prevent a “skin” from forming.

Refrigerate until thoroughly chilled, at least 1 hour.

Spread lime custard evenly in graham cracker pie shell, full cooled.

Top with whipped cream before serving.

Heat oven to 350°F.

In medium bowl, stir all ingredients until well mixed.

Reserve 3 tablespoons crumb mixture for garnishing top of pie before serving, if desired.

Press remaining mixture firmly and evenly against bottom and side of pie plate.

Bake about 10 minutes or until light brown; cool on cooling rack.