Makes 12. Process acorns: peel, split, boil twice for 5 mins each in fresh water, drain and break into small pieces. Fry 1 finely chopped red onion until slightly caramelised. Mix with 200g processed acorns, 200g broken cobnuts, 200g crumbled feta, 60 elderberries, 20 chopped blackberries and 1 beaten egg. Season with salt and pepper. Cut filo pastry sheets into 25x25cm squares. Place a twelfth of filling in a 10cm line across the bottom of a sheet, roll up to halfway, fold in edges, roll completely, seal with egg. Wrap in a second pastry sheet same way. Deep fry at 180C until light brown and crisp. Drain and serve warm.