1. Cream butter & sugar until fluffy, add eggs one at a time.
2. Process boiled peeled chestnuts in food processor until a fine meal is produced.
3. Add to mixture with orange zest and enough orange juice to create a cake batter consistency.
4. Pour into a cake tin lined with baking paper.
5. Bake at 170°C for 30 mins or until an inserted skewer comes out clean.