In a saucepan on low heat, combine marshmallows and milk. Cook until marshmallows are melted, and mixture starts to boil. Remove from heat.
In a large bowl, beat cream cheese until smooth. Stir in egg yolk. Fold in 1/3 of the melted marshmallow mixture, then quickly fold in remaining marshmallow until no streaks remain. Stir in lemon juice.
In a large bowl, beat cream until soft peaks form. Fold the whipped cream into the cream cheese mixture until no streaks remain. Spread into graham crust. Refrigerate for 3 hours.