Preheat oven to 350 degrees
Flour, grease and parchment 3 x 7inch cake pans, set aside.
CAKE:
In bowl of mixer add the sugar, flour, cocoa powder, baking powder, baking soda and salt. Mix to combine.
Add in the eggs, milk, oil and vanilla, mix on medium speed about 2 minutes.
With mixer on low slowly stream in the boiling water. Continue mixing until all ingredients are incorporated.
Scrape sides and bottom of bowl to release any clumps and mix well into batter. Batter will be runny, this is ok.
Pour evenly into prepared pans. Bake 45-50 minutes or until toothpick comes out clean.
Let cool completely.
BUTTERCREAM:
Combine sugar, egg whites, in medium sauce pan.
Whisk until sugar is dissolved, 2 to 3 minutes. Test by rubbing between your fingers; the mixture should feel smooth.
Pour mixture into bowl of mixer fitted with whisk attachment.
Mix egg white mixture until frosty, add the cream of tarter.
Mix egg whites again on med/high until glossy, stiff peaks form and mixture has cooled.
Reduce speed to medium and add butter 2 tablespoons at a time, mix until well incorporated. (mixture may appear curdled, keep mixing.)
Add in the vanilla extract. Mix well to combine.
Switch to the paddle attachment.
Mix on medium/high speed to smooth buttercream for about 2 minutes.
ASSEMBLY:
Cut cake layers horizontally to equal six cake layers.
Lay first cake layer on cake plate.
Add layer of buttercream, I used a piping bag.
Repeat with remaining layers, adding layer of buttercream between each.
Crumb coat the cake on the sides and top. This is a "naked cake" so a crumb coat is all I did. Refrigerate for 30 minutes to an hour.
Garnish with fresh flowers or however you like.
Set in a cool place until ready to serve.
If traveling with this cake I would recommend refrigerating it for at least an hour. This will firm up the buttercream and make it less likely to smudge if lightly dinged.