1Step 1
Preheat the oven to 350°F and bring all ingredients to room temperature. Grease your cake pan.
2Step 2
Whisk together thoroughly cake flour, baking powder, and salt.
3Step 3
Over hot water, melt unsweetened chocolate and add boiling water.
4Step 4
In a large bowl, beat butter at a high speed until creamy.
5Step 5
Add sugar to the bowl and beat until light and fluffy, about five minutes.
6Step 6
Beat in egg yolks, one at a time.
7Step 7
Add the cooled chocolate mixture.
8Step 8
Beating at a low speed, add the flour mixture to the butter mixture in three parts, alternating with the milk. Beat batter until smooth after each addition. Add vanilla.
9Step 9
Using clean beaters, in a large bowl beat egg whites at a medium-high speed until they are stiff but not dry. Fold them lightly into the batter.
10Step 10
Scrape batter into a prepared pan and bake until a cake tester inserted into the center comes out clean, approximately 30 minutes. Let cool before frosting.