1. Preheat the oven to 180°C/350°F.
2. Start by melting the 300g (1 1/3 cups) chocolate and butter together until soft and silky, either in a double boiler or microwave. In a separate bowl mix the sugar, eggs, and cocoa powder; fold in the buttery chocolate mix and stir until it all comes together.
3. Pour into your favorite oiled cake tin (I used a buttered 8-inch springform pan). Place this tin in another deep dish, which you will now fill with hot water so that you can bake the cake evenly in a water bath. (I wrapped the bottom of my springform pan in foil before placing it in the water bath.)
4. Carefully place this into the oven and bake for 35-45 minutes depending on your oven and the thickness of your tins (in the springform pan, my cake actually took 90 minutes to bake because it was so thick!).
5. When baked, let the cake rest awhile; often the cake is better the next day.
6. You can add any frosting you like (or do what I did: dust it with powdered sugar) but we like to smother this cake with rich chocolate ganache and toasted almonds.
7. To make the ganache melt together the 250g (1 cup) of chocolate and 25 g (1 stick) of butter, then stir in the cream. You will notice the consistency change to a thick chocolate goo. Spread this evenly onto the cooled cake and then lick the bowl, spreading chocolate goo all over your face, hair, and new top (is that pretty much the best sentence you've seen in a recipe or what??)
8. Top the cake with your favorite toasted nuts like almonds, walnuts, or hazelnuts, or go mad with some glazed fruits for color.