Ever since I saw Martha's Birthday Cake in her Baking Handbook I have wanted to make a domed cake. But hers is almond with meringue, and my family is just not keen on almond and meringue.
So here's what I did instead:
1. Prepare a batter for a regular 9 inch layer cake. (I used a recipe from Cook's Illustrated, but honestly you could use a mix or whatever you like. Although the Cook's Illustrated "Old Fashoned Layer Cake" was seriously excellent.)
2. Bake the cake in a stainless steel bowl (greased and floured) that is 9 inches in diameter and about 4-5 inches deep. The recipe I followed had a baking time of 35-40 mins. In the bowl it took 1 hour and 30 mins - not quite 3 times the original cooking length. I started checking it after an hour though. Let it cool for about 10 mins in the bowl, then let cool on a rack.
3. Slice the cake into 3 or 4 layers - it really depends on how tall your cake is and how good you are at slicing. I used my bread knife to do this and I knew I couldn't make the slices quite level, so I drew a line with icing on the side of the cake. Then when I reassembled I used the line to reposition the layers correctly.
I filled the cake with kahlua butter cream icing. I reduced the kahlua first to intensify the coffee taste and cook out a little of the alcohol. I then covered the cake with chocolate ganache. Overall, while the entire process was time consuming, it was not very difficult. I think this domed shape would also work well for children's parties - you could decorate the dome to look like turtle or a hedgehog.
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The cake was a huge hit - everyone liked it better than the one I made a couple weeks ago. The one thing I would do different next time is not used a poured icing. Once the cake was assembled it wasn't quite smooth so it wasn't quite as fantastic looking as one might like.