Place the whole oranges in a saucepan and cover with cold water.
Bring to the boil over a medium-high heat, then reduce the heat to low. Cover with a cartouche (a round of baking paper) to keep the oranges submerged and simmer for 1–11⁄2 hours, topping up the water if necessary, until soft.
Preheat the oven to 180°C (160°C fan bake). Line a 22cm-diameter round springform cake tin with baking paper.
Remove the oranges from the saucepan and cool slightly.
Quarter each orange and discard the pips. Place the orange quarters in a food processor and blitz to a smooth purée.
Add the ground almonds, sugar, cocoa, baking powder, baking soda and eggs. Pulse to combine.
Pour into the prepared cake tin and bake for 45 minutes or until a skewer comes out clean. Cool in the tin for 10 minutes, then transfer to a rack to cool completely.
Dust with cocoa and serve with ice cream and oranges.
A Table at Tangleby
In this exceptional book, it shares more than 170 delicious dishes, from simple snacks to dinner parties that are guaranteed to impress your guests.