In a milk pan, melt the marshmallows in milk over low heat. Let cool it slightly.
Crush the graham crackers, mix in the melted butter and put into the pie plate. Press with your hand. Keep in the refrigerate for about 30 min.
Add the sugar to the heavy cream and whip it.
Fold the marshmallow mixture into the whipped cream then add the lemon juice.
Pour it into the pie plate. Let it cool in the refrigerate at least 3 hours.