Happy Birthday, part 2: The Birthday Cake

Even though HH's birthday was last Tuesday, I'm just now getting around to blogging about his birthday cake. It's not sooo late -- we just ate the last piece tonight!

I'd been eying this "Hot Chocolate Layer Cake" ever since I bought the magazine with it on the cover back in November on our way down to Cancun. But you really need a special occasion to make something so decadent, and HH's birthday provided that opportunity, as did his birthday last year for the Chocolate Stout Cake.

I've decided to maybe try making him a different chocolate cake every year for his birthday. Why? Because I can, and because he's great.

Anyway, a couple of preliminaries about this hot chocolate layer cake. First, all of the reviews online said it was so ridiculously rich that not even the chocolate lovers could finish a piece. So, I decided to cut the recipe in half (I hand-write all of the amounts in the recipe so I don't accidentally forget and add to much salt or oil). It made a nice, 3" deep cake (plus another inch for the frosting!); I thought it was just right.

Also, I like my Thomas Keller marshmallow recipe, so I decided to use that instead of the recipe they gave in the magazine. If it ain't broke... Wait, what??? I haven't blogged about homemade marshmallows? My friends, I've been holding back on you. They are like little pillows of deliciousness, completely different in flavor and texture than the store bought ones ... and by "different" here, I mean, "totally, awesome-ly better."

This is going to be a long post, so I'll cut to the chase... but just one more thing. One of the commenters said that they thought the marshmallows on top were gimmicky. I beg to differ. We took this cake to a sushi restaurant and ate it for dessert, and the marshmallows were a bit like vanilla ice cream for this chocolate cake, except they didn't melt. I totally dig the "chocolate cake and marshmallow combo."

Oh, and the frosting -- because it is whipped -- is light and delicious. I dug it, too. More precisely, I dug into it. But enough of that. Without further ado... here is the recipe!

For the cake

6 oz. (3/4 cup) unsalted butter; more for the pans
13-1/2 oz. (3 cups) unbleached all-purpose flour; more for the pans
3/4 cup canola oil
4-1/2 oz. bittersweet chocolate, finely chopped
3 cups granulated sugar
2-1/4 oz. (3/4 cup) natural unsweetened cocoa powder
3 large eggs, at room temperature
3/4 cup buttermilk, at room temperature
2 Tbs. pure vanilla extract
2-1/2 tsp. baking soda
1/2 tsp. kosher salt

For the frosting
2-1/2 cups heavy cream
3 oz. (6 Tbs.) unsalted butter
1 vanilla bean, split lengthwise and seeds scraped out
6 oz. bittersweet chocolate, finely chopped
2 cups granulated sugar
6 oz. (2 cups) natural unsweetened cocoa powder; more for decorating
1/2 cup Lyle’s Golden Syrup [I couldn't find Golden Syrup -- which I now know is condensed cane syrup -- so I used dark karo syrup. It worked, and I'd probably use it again because when I found Lyle's at World Market, it was pretty pricey.]
1/4 tsp. kosher salt

For the marshmallows (I'm omitting this part because you can check out Keller's recipe. Or link back to this original recipe.)

Make the cake

Position racks in the bottom and top thirds of the oven and heat the oven to 350°F. Butter three 9x2-inch round cake pans and line each with a parchment round. Butter the parchment, then dust with flour and knock out the excess.

In a 3-quart saucepan, combine the butter, oil, chopped chocolate, and 1 cup water. Heat over medium heat until melted.

In a large bowl, whisk the flour, sugar, and cocoa powder. Pour the hot chocolate mixture into the sugar mixture and whisk until combined.
Whisk in the eggs, one at a time, then whisk in the buttermilk, vanilla, baking soda, and salt. Divide the batter evenly among the prepared pans.

Set two pans on the top rack and the third on the lower rack. Stagger the pans on the oven racks so that no pan is directly over another. Bake, swapping and rotating the pans’ positions after 20 minutes, until a toothpick inserted in the center of each cake comes out clean, 35 to 40 minutes. Cool on racks for 10 minutes. Invert the cakes onto the racks, remove the parchment, and cool completely.

Make the frosting

In a 4-quart saucepan over low heat, combine the cream, butter, and vanilla bean and seeds and stir until the butter is melted. Remove the vanilla bean and whisk in the chopped chocolate until melted. Whisk in the sugar, cocoa powder, syrup, and salt until smooth—be sure the cocoa powder dissolves completely. Pour into a 9x13-inch pan and freeze until firm, about 2 hours, or refrigerate overnight.

Assemble the cake

Remove the frosting from the freezer or refrigerator. Transfer to the bowl of a stand mixer fitted with the paddle attachment and beat on medium speed for 2 minutes to soften. Change to a whisk attachment and beat at medium-high speed until light and fluffy, about 3 minutes.

Put a cake layer on a flat serving platter or a cake stand lined with strips of waxed paper to keep it clean while icing. Top the layer with 1-1/2 cups of the frosting, spreading it evenly with an offset spatula to the cake’s edge. Repeat with another cake layer and 1-1/2 cups frosting. Top with the last cake layer.

Put 1-1/2 cups of the frosting in a small bowl. With an offset spatula, spread this frosting in a thin layer over the top and sides of the cake. Refrigerate the cake until the frosting firms enough to seal in the crumbs, 20 to 30 minutes.

Spread the remaining frosting in a smooth layer over the top and sides of the cake. If necessary, you can rewhip the remaining frosting to loosen and lighten it. Remove the waxed paper strips.

Use the foil overhang to lift the marshmallow from the pan. Using a knife that has been dipped in cold water, cut along the edge of the marshmallow to release it from the foil. Transfer to a cutting board and remove the foil. Put the remaining 1 cup confectioners’ sugar in a medium bowl. Cut the marshmallow into cubes of different sizes, from 1/4 to 3/4 inch (you will need to continue to dip the knife in cold water as you cut the marshmallows). The marshmallows will be very sticky—dip the cut edges in the confectioners’ sugar to make them easier to handle. As you work, toss a few cubes at a time in the sugar to coat, then shake in a strainer to remove the excess. Mound the marshmallows on top of the cake (you’ll need only a third to half of them). Sift some cocoa powder over the marshmallows.

Make Ahead Tips

You can bake, cool, wrap, and store the cake layers at room temperature for up to 1 day or freeze for up to 1 month. You can refrigerate the frosting for up to 3 days. The assembled cake can be refrigerated for up to 4 hours (return to room temperature before serving). Wrapped well, leftover marshmallows keep at room temperature for up to 1 month.