For filling, melt marshmallows in milk in the top of a double boiler. Cool thoroughly.
Fold in whipped cream and spread over crust. Chill.
Combine raspberries, 1 c. water, sugar and lemon juice in heavy pan. Heat to boiling.
Dissolve cornstarch in ¼ c. cold water and slowly stir into raspberry mixture.
Cook, stirring constantly until thickened.
Cool thoroughly and gently spread over marshmallow layer.