Unfortunately, my experiment with a rolled cake did not go well. I’m not sure where exactly the problem was, but when I rolled the cake, it got lots and lots of gashes in it. It might have been that I over-baked the cake a little, or maybe it was my baking powder, which is on the old side. Whatever the problem was, the result was a rolled cake with lots of gashes in it revealing the gooey frosting core. Fortunately, these were in part hidden by the chocolate glaze that went on top (I seem to be hiding lots of my mistakes by pilling other, reliable things on top of them, see my previous post). Ultimately, the cake didn’t look very good, but was absolutely delicious.
I think before I make a roll cake again, I will consult some more experienced friends and see what they recommend. In retrospect the wise thing to do would have been to cut the sheet cake in half, and just made a regular layer cake. Oh well. Also, if I were going to serve this to people right away, I would just scoop it into bowls, mix it up, poured the chocolate over it and called it a trifle, no one would know the difference, and it would be just as good. If you want to see what this thing would look like if it turned out right, head over to tartlette.
For the cake:1 stick butter
2 tsp instant coffee
3/4 cup water
3/4 cup chocolate
1 cup sugar
1 1/4 cup all purpose flour
1 tsp baking powder
2 Tb cocoa powder
Line a baking sheet with parchment paper, lightly coat with cooking spray. Pour the chocolate cake batter in the baking sheet and bake for 15-20 minutes at 375F. Do not overbake or it will crack when you roll it. Check after 12-15 minutes, if it springs back when you touch it, it's done.
Remove from the heat, cover with a towel and let cool a few minutes.
Cover with a sheet of parchment paper and unmold on the kitchen counter. Peel the bottom parchment layer that is now your top, roll the cake without filling with the parchment paper from the long side to give it some form and elasticity for when you fill it with the buttercream. Let cool completely. Sadly my cake split pretty bad when I rolled it. Also, make sure it cools completely, or the buttercream will melt as you put it on, causing it to slop out.
1 cup sugar
1/2 cup water
4 sticks of butter (don't roll your eyes, you won't feel it:)) Butter should be soft but nor mushy (65F)
1 Tb vanilla bean paste
2 Tb instant coffee dissolved in 1 Tb hot water
In a stand mixer or with a hand held one, whip the egg yolks for a minute.
Boil water and sugar until the temperature reaches 238F on a candy thermometer.
Beat in the softened butter until the buttercream is smooth and together. Add the vanilla bean paste and the coffee, beat a few extra seconds until incorporated.
For the ganache:
3/4 cup heavy cream
Bring the cream to a boil in a heavy saucepan. Pour over the chocolate. Let stand a couple of minutes and then stir carefully until it is incorporated and smooth.
Unroll the cake from the parchment paper, fill with the buttercream (you won't use it all). Reroll the cake, and set it wire rack set over a piece of parchment paper. Cover with the ganache and douse with chocolate sprinkles. Refrigerate to set. Here's what mine ended up looking like, like I said not pretty.