Instructions

1. 1
   Butter a 9 in (22 cm) pan and line bottom with parchment paper. Preheat oven to 325°F (163°C or Gas Mark 3).
2. 2
   Melt chocolate in microwave, remove, and let cool, while stirring often.
3. 3
   Beat butter in mixer, then, on low, add confectioners sugar. Return to high, beat for 2 more minutes, beat in egg yolks one at a time, then add chocolate and vanilla.
4. 4
   Whisk egg whites and granulated sugar together in a bowl. Stir 1 quarter of it into the chocolate mix, then fold in the rest.
5. 5
   Sift half the flour into mixture, fold in, and repeat with remaining flour.
6. 6
   Spread evenly in pan, then bake for about 45 minutes.
7. 7
   Let cool 10 minutes, then remove from pan.
8. 8
   Glaze and frost cake to your liking.