I'm really not sure if it was my substitution of a chocolate bar instead of chips, an extra 1/4 cup of evaporated milk or just a sketchy recipe but what I had hoped would become fudge turned out to be the best fudge frosting ever.
Matt and I love chocolate, and our mutual favorite chocolate fix is Chocolate Sambuca Cake from Buca de Beppo (recently renamed "double dark chocolate cake"...whatever). It has fudge-like icing on top of a rich chocolate cake served with a spicy sambuca chocolate sauce, absolutely divine. When I found myself with mushy, icing-like fudge, I immediately set forth on a mission to make my own Chocolate Sambuca Cake, sans sambuca sauce (I'm not buying a bottle of aniseed-flavored liquor just for this, plus I ran out of butter).
I have made chocolate cakes that call for cocoa powder, and I have made chocolate cakes with all-purpose flour instead of cake. It never came out well. This time I found a recipe that called for unsweetened baking chocolate squares and I used real cake flour: it's hands down the best made-from-scratch chocolate cake I've EVER made.
Most importantly, I thoroughly enjoyed every step of making this chocolate cake. It was not easy, but it was worth all of the effort. The internet is flooded with quick-and-easy recipes that will take far less time than this, but I guarantee this rich, chocolate cake is worth it, and it's a fun way to spend an afternoon in your kitchen. The genius of this cake is in the details: using hot coffee instead of boiling water and adding a dash of mace adds complexity and depth to the rich, chocolaty flavor.
Chocolate Heaven Cake
This recipe is for one tall 9" cake, a 2-layer 6 - 8" cake, or 12 cupcakes. The quantities easily double for a two layer 9" cake.
3 squares unsweetened chocolate
1/4 cup butter
1-1/4 cup sifted cake flour
1-1/4 cup sugar
1 teaspoon baking soda
1/2 cup sour cream (or butter milk, or milk with 1 tsp. vinegar)
3/4 cup hot coffee*
2 large eggs
1 tsp vanilla extract
Unwrap your chocolate squares and cut a couple of times with a sharp knife. Use the wrapper to pour it into a microwave-safe bowl. Slice 1/4 cup of butter onto the top of the chocolate. Microwave at power level 6/60% for 90 seconds to 2 minutes. Stir until most of the chocolate is melted.
Pour very hot, fresh coffee onto the top of your melting chocolate. Stir until all is melted.
In a separate large bowl, cream butter and sugar with an electric mixer. Add eggs, mix until blended, then add sour cream, vanilla and a pinch of mace. Mix in your chocolate-coffee mix until blended.
Now aren't you glad you got that complete set of nested mixing bowls? It's time to whip out a third one for the dry ingredients. Start by sifting your cake flour directly into a measuring cup until you get to 1-1/4, then add baking soda and salt and whisk until well-blended. Slowly add your dry ingredients to your wet ingredients while mixing at low speed--stop right when your batter is smooth. (I stopped a little early and had a floury lumps in my otherwise perfect cake, but it's best to err on the side of under-mixed: too much mixing will make the flour do uncakelike things).
*One of the numerous "errors" I made when making this forgiving cake was doubling the hot coffee. It came out very dense and moist and it did not poof up...if you want a spongy or fluffy cake, reduce the liquid.
While your cake is baking, prepare the frosting.
1/4" cup butter
4 ounces 70% cocoa chocolate bar or dark chocolate chips
1/2 cup marshmallow cream (this is 1/4 of a jar of 7 ounces of cream)
1/4 teaspoon vanilla extract
1/4 cup + 3 Tablespoons evaporated milk (1/4 a 14 ounce can)
1 cup white sugar
Set up a double boiler (metal bowl over water or steam). If you are brave and you have a very heavy pan that distributes heat well, you can skip the double boiler and use very low heat and a lot of patience: heating too quickly will ruin it.
Put evaporated milk, sliced butter, and sugar in your metal bowl. Heat very slowly, 6 - 12 minutes, until your candy thermometer reads 236 degrees. While heating, crush the chocolate bar. Immediately remove from heat, add chocolate and stir until melted, then stir in vanilla and marshmallow cream.
If you plan to transfer your frosting to a storage container do so now before it hardens and becomes difficult. If it's all going on your cake, just place the metal bowl in the fridge.
Allow your cake and your frosting to cool for about 30 minutes before applying. Room temperature frosting on a chilled cake is ideal. Don't bother trying to smooth down the unruly frosting: use the back of a spoon to make lots of wild swirls and peaks. Serve cake chilled for maximum fudge-like frosting.