Dark Chocolate Ganache

Put the chocolate chips in a large heatproof bowl. Bring the cream to a boil in a medium saucepan. Just before the cream comes to a full boil, pour the cream into the chocolate chips and whisk together until smooth. Add the butter and stir until smooth and shiny. Place plastic wrap directly over the surface to prevent a skin from forming, then let stand at room temperature overnight to cool. Store in the refrigerator, covered, for up to three weeks.