Preheat oven to 350F, grease two 8" round baking pans and dust with cocoa powder. Line bottoms with parchment.
Place all dry ingredients into the bowl of a stand mixer fitted with a paddle attachment. Stir to combine.
In a medium bowl whisk all wet ingredients (pour hot water in slowly as not to cook the eggs).
Add wet ingredients to dry and mix on medium for 2-3 mins. Batter will be very thin.
Pour evenly into prepared pans. I used a kitchen scale to ensure the batter is evenly distributed.
Bake for 45 mins or until a cake tester comes out mostly clean.
Cool 10 minutes in the pans then turn out onto a wire rack to cool completely.
French Silk Frosting:
Using a stand mixer fitted with a paddle attachment, beat butter and sugar until pale & fluffy (approx. 3 mins). Ideally use a a chilled bowl*. Scrape bowl as needed.
Add cooled melted chocolate and vanilla, whip until combined. Scrape bowl as needed.
Switch to whisk attachment. Add eggs one at a time, whipping for 5 mins after each addition. Scrape bowl before adding each egg.**
Frosting will be fairly runny. Place entire bowl with whisk into the fridge to chill for 30mins (take out to whip every 10mins).
You can either serve them like this, as two separate cakes, or place both in the fridge to chill for 1 hour, then carefully remove one from the cake board stack on top of the other.
Notes
This recipe uses raw eggs which may be an issue for some. I recommend using pasteurized eggs. Raw eggs should not be consumed by pregnant women, small children, or anyone with health issues.* A cold bowl will help the frosting whip up better. ** Do not skimp on this! It takes a long time, but this is what helps give it the proper texture. *** You will have a bit of frosting left over. You can use this to add more frosting to the cake if desired, or spoon into small bowls and serve as mousse.French Silk Pie filling recipe from Martha Stewart.