2 ounces unsweetened chocolate
3 tablespoons water
cocoa powder for dusting pans
for the buttercream:
Preheat oven to 350 degrees.
Grease two 8-inch layer cake pans; dust pans with cocoa powder. Set pans aside.
Whisk together flour, baking soda, cream of tartar and salt. Set aside.
Combine 3 tablespoons water with unsweetened chocolate and microwave until melted. Be careful not to burn. (I microwave for about 15 seconds a clip and give chocolate a good stir every time I check the bowl.) Once melted, set chocolate aside.
Cream butter and granulated sugar in bowl of stand mixer for 4-5 minutes.
Meanwhile, beat 4 egg WHITES in separate bowl until fluffy white clouds. Set whites aside.
Add vanilla and 4 egg yolks to bowl with butter/sugar, mixing to combine. Stir in melted chocolate.
Add flour mixture to the party alternately with milk, mixing to combine.
Fold beaten egg whites into batter until thoroughly combined.
Pour batter into prepared layer cake pans and bake in preheated oven for 45-50 minutes. Cakes are done when sides pull away from edge of pans and cake tester (or toothpick) comes out clean after inserted into center of cake.
Place cakes (still in their pans) on wire rack to cool for about 10 minutes. Then invert cakes onto rack and let cool completely before frosting.
For the Chocolate Buttercream:
Beat softened butter with confectioners’ sugar for at least 5 minutes, scraping down sides of bowl every so often.
Add vanilla, melted chocolate and milk (a tablespoon or two at a time — honestly, I didn’t measure) and continue beating (like you mean it) — and continuously scraping down sides of bowl to catch any globular goodness — until you have a fluffy, spreadable, super-delicious buttercream.
Frosting the layers:
Lay 4 strips of parchment paper or aluminum foil on cake plate, where the edges of the first cake layer will rest. (You will remove these strips post-frosting.)
Place one cake layer atop strips.
Dollop a modest scoop of buttercream onto the layer, frosting in broad strokes to seal up any wayward crumb-age, then dollop a a generous scoop and liberally frost layer.
Place second cake layer atop first. Frost the top generously before frosting the sides of the cake. Don’t be stingy. Use all the buttercream to adorn the cake, swirling in carefree strokes as you go. (Again, this cake is not about perfection. The layers are not perfectly even, and the frosting shouldn’t be, either.)
Remove the strips of parchment.
Gobble up a slice of moist perfection with a tall, icy glass of milk.