When poured over ice cream, this chocolate sauce hardens into a shell that can be broken with the back of a spoon into tasty chocolate shards.

Combine in a double boiler or heatproof bowl set over a pan of barely simmering water:

Stir frequently until the chocolate is fully melted. Let cool slightly and use right away or transfer to a dry container and store at room temperature. To remelt the chocolate, either transfer the mixture to a double boiler and melt over simmering water, or microwave in 30-second bursts, stirring after each one, until fully melted.