I based this recipe on this recipe by Sally’s Baking Addiction

1. Pre-heat the oven to 180 degrees Celsius (350 F).
2. Take a 8-inch round cake tin. Cover the sides and bottom with baking parchment. Grease the baking parchment, otherwise the cake will stick.
3. Cut the butter into cubes and break the chocolate into pieces, if you use a chocolate bar. Put this together into a glass bowl. Melt in the microwave in bursts of 30 seconds. Stir together and repeat for 30 seconds. Repeat until everything has melted. Put aside to cool down for 2 minutes.
4. Add sugar, espresso powder and vanilla extract to the melted chocolate and stir together with a whisk.
5. Add the eggs and whisk well.
6. Finally add the cacao powder and a pinch of salt. Mix together with a whisk.
7. Pour the mixture into the baking tin.
8. Bake the cake in the oven for 30 minutes. Some ovens bake quicker than others, so check about 5 minutes before the end of the baking time if the cake is done. The cake is done when a toothpick comes out clean.
9. Leave the cake to cool down in the tin for 10 minutes. Carefully take it out of the tin and put onto a plate. Leave to cool down to room temperature and then put it into the fridge for a few hours.
10. I love to serve this cake with some icing sugar on top and fresh raspberries. Also delicious with a dollop of lactose-free whipping cream.