While cupcakes are baking melt chocolate, butter and water in top of double boiler over low heat whisking constantly until melted and uniform. (guittard.com)
* To melt chocolate: In double boiler over low heat, heat chocolate stirring constantly, until melted. (styleathome.com)
Combine all ingredients except walnuts in top of double boiler over low heat, stirring frequently until melted and smooth. (guittard.com)