180 grams of semi-sweet chocolate
3/4 cups of flour
3/4 cups of sugar
1/3 cups of melted butter
1 tablespoon of rhum
For the icing:
1 teaspoon of cocoa powder
1/6 cups melted butter
1/2 cups of icing sugar
2 tablespoons of strong espresso coffee
Preheat your oven to 325 degrees celsius. Melt the chocolate in a double boiler making sure the chocolate melts slowly so it does not burn. You can add 1 teaspoon of water if the chocolate does not appear to be melting smoothly. While the chocolate is melting, beat the 4 egg yolks and sugar until the mixture whitens (this takes a few minutes). In a separate bowl, whisk the egg whites with a pinch of salt until they become very stiff.
Add the swifted flour and rhum to the sugar mixture. Add the melted butter to the chocolate, and pour into the sugar mixture. Whisk until the mixture is homogenous. Add the egg whites by folding them in with a flat spatula trying not to break them. Fold until the mixture turns into an even mix. Pour the mixture into a buttered cake mold or baking dish.
Bake the cake for 30 to 40 minutes. The cooking time really depends on your oven, but the cake should slightly rise, and the center should still look a little moist. The rest of the cake should look just cooked. Once the cake is cooked, allow to cool. While it does, make the icing. Mix the melted butter and the swifted icing sugar, and add the espresso and cocoa. Beat with a fork until smooth. The icing should not be too liquid or it will not stick to the cake - if it is, add a teaspoon or so of icing sugar and stir again.
You can be as creative as you want to ice the cake - we used a small ziploc bag, filled it with the icing, sealed it and then cut out a small corner at the bottom of it. Using your fingers, carefully block the corner so the icing comes out slowly and decorate the top of the cake. You can also just use a spatula to apply the icing to the top of the cake in a uniform layer. I would suggest not putting too much icing though, because the cake is already quite rich!