INGREDIENTS

Cake: Weighing your ingredients vs. measuring gives you the best results:
• 1 1/2 cups (180 g/6 oz) all-purpose flour
• 1 1/3 cups (275 g/10 oz) sugar
• 1/2 cup (60 g/2 oz) dark cocoa powder
• 1 1/4 teaspoons (6 g) baking soda
• 1 1/4 teaspoons (5 g) baking powder
• 1 teaspoon (5 g) salt
• 75 mL (2.5 liquid oz) vegetable oil
• 140 mL (5 liquid oz) buttermilk
• 130 mL (4.5 liquid oz) espresso or strong, hot brewed coffee
• 2 eggs, room temperature, lightly beaten
• 1 tablespoon (15 mL) vanilla
Swiss Buttercream Frosting:
• 5 large, fresh egg whites (150 g/5 oz)
• 1 1/4 cups (250 g/9 oz) sugar
• 3/4 lb (3 sticks/340 g/12 oz) butter, cut into cubes and cool, but not cold
• 2 teaspoons (10 mL) pure vanilla extract
• Pinch of salt

METHOD

Cake:
1. Preheat oven to 350° F (180°C). Prepare three 6-inch round cake pans with butter, parchment paper rounds, and cocoa powder. Tap out excess.
2. In bowl of electric mixer, sift all dry ingredients. Add all remaining ingredients to bowl with the dry ingredients and with paddle attachment on mixer, mix for 2 minutes on medium speed (you may need the plastic splash-guard that comes with mixer) and pour into prepared pans. If possible, use digital kitchen scale and weigh pans for even layers. Batter will be liquidy.
3. Bake for 20 minutes and rotate pans in oven. Cakes are done when toothpick or skewer comes clean--approximately 30 minutes. Try not to over bake.
4. Cool on wire racks for 20 minutes then gently invert onto racks until completely cool.
Vanilla Swiss Meringue Buttercream
5. Yield: ~5 cups
6. Wipe the bowl of an electric mixer with paper towel and lemon juice, to remove any trace of grease.
7. Add egg whites and sugar, and simmer over a pot of water (not boiling), whisking constantly but gently, until temperature reaches 150°F, or if you don't have a candy thermometer, until the sugar has completely dissolved and the egg whites are hot.
8. With whisk attachment of mixer, begin to whip until the meringue is thick, glossy, and the bottom of the bowl feels neutral to the touch (this can take up to 10 minutes or so). *Don't begin adding butter until the bottom of the bowl feels neutral, and not warm.
9. Switch over to paddle attachment and, with mixer on low speed, add butter cubes, one 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). *If mixture is too runny, refrigerate for about 15 minutes and continue mixing with paddle attachment until it comes together.
10. Add vanilla and salt, continuing to beat on low speed until well combined.
11. Stir the mixture using a rubber spatula until melted and smooth.
Assembly of the 6-Layer Dark Chocolate & Vanilla Buttercream Cake
12. Slice the 1st cake layer in half horizontally, using a large serrated knife and place cut side up on your cake board, pedestal, or plate.
13. Using a small offset palette knife, spread approximately 1/2 cup of buttercream evenly on the top.
14. Repeat this 1-2 until you come to the final layer, which you will place face down on the top of the cake.
15. Place cake on a turntable (if possible), and using a small offset palette knife for the top of the cake, and medium straight palette knife for the sides, cover the cake in a thin layer of buttercream to seal in crumbs. Refrigerate for 30 minutes (or more). *This does not need to be perfect, as that will come with the top "coat" of buttercream.
16. Repeat step 4, and, for best results, use bench scraper held at 90° against the side of the cake, slowly turning the turntable and keeping your hand steady--let the turntable do the work. Clean up edges with your small offset palette knife.
17. Chill cake.
18. *Bring to room temperature before serving--about 2+ hours. Never serve Swiss Meringue Buttercream until it is soft and room temperature. (Adapted from Sweetapolita's recipe)