My SO and I discovered the recipe for our lemon butter frosting when we were just starting to bake cakes; we like it so much that we frost more than half the cakes we bake with that frosting. Sadly, we haven't had as much luck with chocolate frosting. Over the years we've tried a number of different recipes, but most were either too gooey, too hard, too granular, or just not chocolatey enough.
All of our trials and tribulations ended, however, when we made Joy of Cooking's chocolate ganache frosting: it's easy to make, tastes like it was made from chocolate truffles (which it functionally is), looks shiny and smooth when frosted onto a cake, and is the perfect silky texture at room temperature. It even holds up to refrigeration well. Since we just baked a cake and frosted it with this frosting tonight, it's this week's end-of-the-week recipe blogging post.
3/4 cup heavy cream
8 ounces semisweet chocolate, chopped into small pieces (we use chocolate chips)
1 tablespoon flavorful liquor (optional; we used rum this time)
1. Bring the heavy cream to a boil in a non-stick pot over medium-high heat, stirring occasionally.
2. Remove the pot from the heat and add the chocolate. Stir until the chocolate has melted into the cream.
3. Let rest, covered, for 10 minutes.
4. Whisk until smooth, and then whisk in the liquor. Let sit at room temperature, stirring occasionally, until it's the proper thickness to frost. In our ~70F kitchen this took about 45 minutes, though it will depend on the surface-area-to-volume ratio of the chocolate in your pan.
5. Frost the cake. Be sure the cake is close to room temperature when you frost it; if it's too hot, the frosting will melt and run off, but if it's too cold, the frosting will congeal instantly.
6. Serve the cake at room temperature.
This recipe makes enough to thinly frost and fill a cake composed of two 9" rounds. It would easily cover a 9" x 13" sheet cake.
Joy reports that you can use either semisweet or bittersweet chocolate for the frosting; we've only used semisweet. Joy also reports that you can use either butter or heavy cream; we've used either all heavy cream or a mixture of heavy cream and butter with good results. This frosting can also be used as a glaze if you pour it onto the cake while the frosting is still quite warm.
I'd suggest frosting the cake while the frosting is still a bit more liquid than a typical butter-based frosting, as then the frosting will flow just a little after you spread it, removing most of your tool marks and leaving your cake looking smooth and shiny.
Rombauer, I. S., M. R. Becker, and E. Becker. 1997. Joy of Cooking. Scribner, NY.