Peel and wash the potatoes and cut them roughly into pieces. Cover and cook in little boiling salted water for about 20 minutes. Wash lemon hot, grate dry, peel into strips with a zest ripper.
Finely chop the zest, except for something to garnish. Halve lemon and squeeze juice. Wash the mint, shake dry, pluck it from the stalks and chop finely, except for a little to garnish. Add peas to the potatoes 5 minutes before the end of the cooking time.
Warm up the milk. Pour the potatoes and peas into a sieve and, except for a few peas for sprinkling, press them through a potato ricer. Add butter, milk, chopped lemon zest and mint and stir in.
Season to taste with salt and lemon juice. Arrange and garnish with lemon zests and mint, sprinkle with peas.