Dark Chocolate Cake

I baked this cake for my nephew's Christmas eve gathering with his Sixth Former friends.   His friends told him 'Nice Cake'.  A very strong chocolaty cake, good for afternoon tea.  Can dust some icing sugar on top of slices of cake for added sweetness.

Ingredients

[use 8" square tin - line the base with greaseproof paper and greased the sides lightly]
150 gm cooking dark chocolate
100 gm butter
100 ml milk
50 gm cocoa powder - sifted
60 gm plain flour - sifted
5 egg yolks 

1. Preheat oven at 180 degrees C.
2. Melt butter and chocolate together in a double boiler until soft and smooth [I steamed for 10 minutes].  Stir in milk and set aside to cool.
3. Add egg yolks to cooled chocolate mixture in a mixing bowl.  Beat to mix well and lightly fold in sifted flours.   Set aside.

5 egg whites

1 tsp cream of tartar

150 gm castor sugar

1. Whisk egg whites until frothy.  Add in cream of tartar and continue to whisk until foamy.
2. Add in sugar in 3 batches and whisk continuously until stiff.
3. Mix egg whites into egg yolk mixture in 3 batches.
4. Pour batter into baking tin.
5. Bake in preheated oven for 25-30 minutes or until cooked.  Test with a skewer.
6. Remove to cool on a wire rack.  Unmold and slice into pieces to serve.