Dark Devil's Food Cake:
1 1/2 cups (3 sticks) unsalted butter, plus more for pans
3/4 cup Cacao Barry Extra Brute (or other premium dark) cocoa powder,
1/2 cup boiling water
2 1/4 cups sugar
1 tablespoon pure vanilla extract
4 large eggs, lightly beaten
2 1/2 cups all-purpose flour
1 teaspoon baking soda
1/2 teaspoon salt
1 cup buttermilk
Preheat oven to 350 F. Butter three 8″ x 2″ round cake pans, line with parchment rounds, and dust with flour, tapping out the excess. Add boiling water to sifted cocoa powder in medium bowl and whisk; set aside to cool.
In a stand mixer fitted with the paddle attachment, beat the butter, sugar, and vanilla on medium-high speed until lighter in color and slightly increased in volume, 3 to 5 minutes. Lower the speed to medium and add the eggs, one at a time, mixing until each is fully incorporated before adding the next.
Sift the flour and baking soda into a medium bowl. Add the salt to the dry ingredients after sifting and whisk together. Whisk buttermilk into cocoa mixture. Alternate dry ingredients and buttermilk into butter mixture, beginning and ending with dry ingredients. Mix until just incorporated, or finish by hand gently.
Divide the batter evenly between the prepared pans. If possible, weigh the batter in each cake pan to ensure even layers. Smooth with small offset palette knife, and bake for about 35 minutes, rotating once after 20 minutes. Cake is done when toothpick or skewer comes barely clean. Try not to over-bake. I tend to under-bake a few moments, so the skewer is a little bit gummy. This works well for a moist chocolate cake (not vanilla). Let pans cool on wire rack for 20 minutes, then invert cakes onto racks, gently, peeling away parchment rounds. Let cool completely.
Swiss Meringue Buttercream Icing:
16 large egg whites (30g each--total 450g, or 2 cups)
4 cups granulated sugar (800g)
5 cups (2.5 lbs, 10 sticks) of unsalted butter, softened but cool, cut into cubes
30 ml (2 tablespoons) pure vanilla extract
1/4 tsp salt
Wipe the bowl of an electric mixer, whisk attachment, small bowl, and whisk with paper towel and lemon juice (or vinegar), to remove any trace of grease. Add egg whites and sugar, and simmer over a pot of water (not boiling), whisking constantly but gently, until temperature reaches 140 degrees F, or if you don't have a candy thermometer, until the sugar has completely dissolved and the egg whites are hot (you can feel a drop in between your fingers to ensure no granules.).
Take off of stove, and place bowl back on electric mixer fitted with whisk attachment, begin to whip until the mixture is thick, glossy, and neutral (you can feel outside of the bowl to test temperature). Switch over to paddle attachment and, while mixing on medium speed continously, add butter one cube at a time until incorporated, and mix until it has reached a silky smooth texture (if curdles, keep mixing and it will come back to smooth). Add vanilla and salt, mix well. You can also add a wide variety of flavourings, extracts, and more. If buttercream is too runny, the butter was possibly too soft--place into the refrigerator for about 15 minutes, then beat again. If still too runny, add a few more cubes of butter and keep beating. Use immediately, or refrigerate/freeze.
Keep in airtight container in refrigerator for up to one week, leaving out at room temperature when needed, rewhipping in mixer for 5 minutes.
Can freeze for up to 6-8 weeks. To thaw, place on counter overnight, and rewhip for 5 minutes with paddle attachment in an electric mixer.
If buttercream still doesn't have its satiny finish after rewhipping, microwave 1/3 of the buttercream for approximately 10 seconds and add to remaining buttercream in mixer bowl, beating for a few moments to incorporate.
The variations are almost endless, but here are some delicious options:
Chocolate Buttercream: Add 300 g (1 1/2 cups before melting) melted bittersweet high quality chocolate (the best you can get--I use Callebaut) for every 5 cups of vanilla Swiss Meringue Buttercream and beat until incorporated.
Strawberry Buttercream (or any other berry version): Add fruit puree to taste (approximately 1/2 cup for 5 cups of SMB).
Vanilla Bean Buttercream: Add 1 tablespoon of Vanilla Bean Paste OR 1 vanilla bean, scraped for every 5 cups of SMB, and beat until incorporated.
You can also add liqueurs, extracts, and other flavourings, as well as any food gel colours to achieve any desired colour. Just a note that SMB has a yellow tone, due to the butter, so it really can't be pure white.