Last week my office underwent a big change when one of my coworkers retired.  She was one of the more senior level people in the office and had always been my go-to human encyclopedia when I needed help on a project.  To send her off well, a big party was thrown and many people came to express their gratitude for her help over the years.

This coworker is known for her chocoholic tendencies, and she always enjoyed when I took my baking projects into the office for others to enjoy.  So, of course I had to make her something chocolate for her last day!  This was a great opportunity for me to tackle one of my more intense chocolate recipes, since I myself am not such a chocolate lover.

I settled on Midnight Sin Chocolate Cake.  I made a few minor tweaks to accommodate what I had on-hand, and it turned out fantastic.  If you are a chocolate lover, this will satisfy your taste buds.  You can’t make this cake if you are in a hurry, due to the fact that you have to let the cake cool completely and allow the mousse to set as well.  As such, I recommend making the cake and mousse on day 1, pop them both the fridge overnight, and then on day 2 you can assemble and make the ganache.  It’s really easy if you stick to this schedule.   I promise you that the recipe below looks long but it’s not that difficult.  Like I said, make the cake and mousse one day and day 2 will be a breeze.

Midnight Sin Chocolate Cake
adapted from Not So Humble Pie

The Cake

2 ¾ c granulated sugar
¾ t salt
¾ c cocoa powder
1 t baking soda
1 c boiling water
1 c vegetable oil
2 t vanilla extract
2 t instant espresso powder or crystals (optional)
1 ¾ c all purpose flour
4 large egg yolks
2 large eggs
¼ c buttermilk

• Preheat your oven to 350°F.
• Spray two 9″ or two 8″cake pans with non-stick cooking spray.  Line the bottoms with parchment to prevent sticking, and then spray the parchment with more non-stick spray.
• In a medium saucepan (but not on the stove), combine the sugar, cocoa, salt, and baking soda. Whisk until combined and then slowly add the boiling water while whisking. Once thoroughly mixed, place the saucepan over medium-high heat and bring to a boil. Remove from heat and allow it to stand for at least 10 minutes.
• After 10 minutes, stir in the instant espresso powder. (I omitted this step/ingredient, and it turned out just fine.  Don’t sweat it.) Add the chocolate mixture to your stand mixer and mix on low speed for about 20 seconds. Add the flour and continue to mix on low until combined. With a minimum amount of beating, add the egg yolks, eggs, vanilla, vegetable oil, and buttermilk. The batter will be very thin.
• Divide the batter between your two pans and bake.  This will take 25-30 minutes for 9″ rounds; add 5-7 minutes for 8″ rounds.  When the center of the cake springs back when you touch it, it’s done.
• Allow the cake to cool for 10 minutes on a wire rack. Run a thin knife around the edge of the cake to loosen and invert onto a flat dish lined with parchment.   Allow to cool completely at room temperature, then wrap the cakes individually in plastic and place them in the refrigerator to chill before assembling.

Frangelico Chocolate Mousse Filling

5 large egg yolks
½ c sugar
1/3 c Frangelico hazelnut liqueur (non-drinkers substitute 1/3 c water)
8 oz bittersweet chocolate (preferably 66% cacao), finely chopped
1 c heavy cream, chilled

• In a heat safe bowl, beat the eggs and sugar together until the mixture is uniform and light in color. Place over a double boiler and whisk until slightly thickened. A ribbon of the egg sugar mixture should flow back into the bowl when the whisk is lifted and the sugar should just be beginning to dissolve. Add the Frangelico (or water) and continue to whisk over the simmering water until the mixture hits roughly 160°F and coats the back of a spoon.
• Remove from heat and add the finely chopped chocolate. Stir until the mixture becomes cool to the touch (roughly 10 minutes).
• Set the chocolate aside and beat the heavy cream to soft peaks. Fold the cream into the chocolate, then cover and chill for at least 4 hours.

Ganache

1 c bittersweet chocolate, chopped (or just use chocolate chips)
1/3 c heavy cream
1 T butter

• **To make life easy, start assembling the cake before you begin to prepare the ganache.  I recommend going through the assembly steps below and making the ganache while the assembled cake is firming up in the fridge (see below).  Then you can pour on the ganache immediately.**
• Put the chocolate in a heat-proof bowl.
• Bring the butter and heavy cream to a low boil over medium-high heat and pour over the chocolate. Give the chocolate a shake to submerge and allow it to stand for 5 minutes without stirring. When the time has passed, gently stir the ganache until smooth.

Assembly

• Place the first cake face up (flat side down) on your dish.  If necessary, even the top out if a mound formed while baking.
• Reserve ¾ cup of the Frangelico Mousse and set aside.  Use the rest of the mousse to create a layer on top of the cake that you just prepared.  Smooth to the edges with an offset spatula or knife.
• Before topping the mousse, check your other (top) cake and see if it needs to be trimmed as well.  Once that is done, lay it top side down (bottom is facing up) on top of the mousse.  Clean up the mousse on the edges, if necessary.
• Briefly refrigerate to allow everything to set.  (**make the ganache now**)
• Pour the ganache on the cake, smoothing over the top with an offset spatula.
• Return the cake to the fridge and allow the ganache to cool.
• Once cool, you can put the finishing touches on the cake. Take the reserved chocolate mouse and fill a piping bag, fitted with a large star tip.  I created several stars of mousse around the perimeter of the cake, but use your imagination.
• Keep the cake chilled until ready to serve. Allow cake to stand for 10 minutes before cutting and serving. Store the cake in the refrigerator, covered to keep it from absorbing odors, for up to 5 days.