Preparation Stir chocolate and butter in medium saucepan over low heat until smooth. Whisk in next 4 ingredients. (Can be made 1 day ahead. Cover and chill.) Stir sauce over low heat until just warm. Whisk cream and powdered sugar in medium bowl to peaks; chill until ready to use. Arrange 2 banana halves in each of 4 long shallow dishes. Add 3 scoops ice cream to each dish. Spoon warm sauce over ice cream. Top with pineapple, whipped cream, and toasted coconut.
Preparation Stir chocolate and butter in medium saucepan over low heat until smooth. Whisk in next 4 ingredients. (Can be made 1 day ahead. Cover and chill.) Stir sauce over low heat until just warm. Whisk cream and powdered sugar in medium bowl to peaks; chill until ready to use. Arrange 2 banana halves in each of 4 long shallow dishes. Add 3 scoops ice cream to each dish. Spoon warm sauce over ice cream. Top with pineapple, whipped cream, and toasted coconut.