Bring milk to boil in double boiler.
Add marshmallows to milk, stir until melted.
Let cool.
Whip cream and flavor with vanilla, then fold into marshmallow mixture.
Add pineapple and nuts.
Sprinkle a dish with graham cracker crumbs.
Pour mixture over it.
Top with crumbs.
Chill overnight.
Serve plain or topped with whipped cream.