1/2 cup semisweet chocolate chips
1/2 cup plus 2/3 cup heavy cream
1/4 cup water
8 marshmallows, cut up
Combine chocolate chips, the 1/2 cup cream, water and marshmallows in a 2-quart saucepan. Cook and stir over low heat until the chocolate and marshmallows melt. Remove from heat; chill thoroughly.
Whip the 2/3 cup cream until stiff. Fold into cold chocolate mixture until well blended. Freeze in ice cube tray; do not stir.