Preheat the oven to 180 degree C. Line a 9″/23cm loose bottomed tin with baking parchment and lightly brush the base and sides with a little oil.
Cook the aubergines by puncturing the skins here and there with a skewer, then placing them in a bowl covered in cling film. Microwave on high for 8 minutes until the vegetables are cooked and limp. Discard any water at the bottom. Leave the aubergines to stand in the bowl until they are cool enough to handle.
Next, skin and puree the aubergines in the blender. Note: I peeled the aubergines before microwaving them with a regular peeler, or you can use the tip of a knife once they are cooked. Once the warm aubergine is pureed and smooth, add the chocolate, which will mingle and melt slowly. Set aside, covered once again in cling film, until all the chocolate has melted. Note: I need to microwave this again for 1 minute covered in cling film, on the lowest setting on the microwave, for the chocolate all to melt.
In a large bowl, whisk up all the other ingredients for a minute until well introduced to each other and slightly bubbly. Fold the melted chocolate and aubergine mixture into the bowl with all the other ingredients.
Pour the mixture into the prepared tin and place it in the bottom of the oven for 30 minutes by which time your kitchen will just sing with the smell of hot chocolate.
Remove the cake from the oven and let it cool in its tin for 15 minutes before turning it out on to a wire rack and peeling off the parchment. Quickly turn it the right way up again and sit it on a plate to avoid any scars from the rack.
Sieve a little cocoa powder over the top of the cake before cutting yourself a slice.