6oz (170 gr)semisweet chocolate, cut into small chunks
1/2C (4 oz) (112 gr)unsalted butter
1/4tspinstant coffee (soluble)(optional)
3/4C (5.30 oz) (150 gr)white sugar
1tsp (0.17 fl oz) (5 ml)vanilla extract
4eggs, big,separated, yolks and whites
1/2tspsalt
Cocoa powder, unsweetened, for decorating
Berries and strawberries, for decorating (optional)
Instructions
Preheat the oven to 356ºF (180°C). Grease and line a round cake pan of approximately 7.90 inches (20 cm) in diameter with parchment paper.
Crack the eggs and place the whites in a clean medium bowl and the yolks in a different small bowl.
Melt the chocolate with the butter, which can be done in two ways. The first is in a double boiler, placing a medium saucepan with plenty of water over medium heat. Then, add both ingredients to a large heat-resistant bowl and place it on top of the pot with water (without touching the water) so that they melt with the steam. The second is in the microwave, adding both ingredients to a large microwave-safe bowl and then melting them for 30-second intervals, i.e., put the bowl in the microwave for 30 seconds and take it out after this time to mix a little with a fork. Repeat the process until both the chocolate and the butter are completely melted.
As soon as the chocolate and butter are melted, add to the same bowl the soluble coffee with half of the sugar and beat with a hand whisk for 1 minute until everything is integrated.
Add the egg yolks one by one, beating a few seconds after each addition. Then add the vanilla extract with the cocoa powder (previously sifted) and beat for 1 more minute until very smooth.
Separately, with an electric mixer, beat the egg whites for 1 minute until they begin to form soft peaks. Add the rest of the sugar with the salt and continue beating for 2-3 more minutes until stiff peaks form.
Carefully add the beaten egg whites in three separate additions to the chocolate mixture. Use a rubber spatula to integrate both mixtures doing folding motions until everything is smooth.
Pour this mixture into the cake pan and bake at 356ºF (180° C) for 25-30 minutes until the cake has risen a little and slightly cracked on the surface, which is normal and part of the charm of this cake.
Once ready, take the cake out of the oven and let it cool down in the pan for 20 minutes. Then carefully run a dull knife around the cake to then turn it out and let it cool completely on a wire rack.
To serve, decorate the cake with a little cocoa on top, plus berries if desired.