Put 225g of finely chopped semisweet chocolate, 1 cup of heavy cream, 1 tablespoon of sugar, and 1 tablespoon of unsalted butter in a microwave-safe bowl.
Microwave on medium power until the cream is hot and the chocolate starts to melt. Stir until smooth, letting the remaining heat melt the rest of the chocolate. Serve warm, with fruit for dipping.
