Cook the potatoes in their skins in boiling lightly salted water until soft. Drain and leave to cool, then chop them in half and peel while still warm.
Place the potatoes in a bowl and mash until smooth. Crumble the feta cheese into potatoes and add the spring onions, dill, egg and lemon juice and season with salt and pepper. (The cheese is salty, so taste before you add salt.) Stir well, until combined.
Cover and chill until firm. Divide the mixture into walnut-sized balls, then flatten them slightly. Dredge with flour, shaking off the excess.
Heat the oil in a large frying pan and fry polpettes in batches until golden brown on both sides. Drain on kitchen paper and serve hot, garnished with spring onions and sprigs of dill, and serve with lemon wedges.
Tip: To save time try the polpettes in advance, cool and chill until required. Reheat in the oven before serving.