|1 heaped tsp
Put the clementines in a pan with some cold water, bring to the boil and cook for 2 hours. Drain and, when cool, cut each clementine in half and remove the pith. Dump the clementines in a blender - skins, pith, fruit and all - and give a quick whir. Then tip in all the remaining ingredients and pulse to a pulp. Preheat the oven to gas mark 5/190ºC. Butter and line a 21cm Springform tin.
Pour the cake mixture into the prepared tin and bake for an hour, when a skewer will come out clean; you'll probably have to cover with foil or greaseproof after about 40 minutes to stop the top burning. Remove from the oven and leave to cool, on a rack, but in the tin. When the cake's cold, you can take it out of the tin.