- Preheat the oven to 200 ° C / Gas 6.
- Bake the potatoes in their skins for 1–1¼ hours until tender the whole way through. Remove the flesh from the skins (ideally while still warm) and mash until smooth – a potato ricer works best here. Mix in the ricotta, a pinch of salt and white pepper and the flour. Make a well in the middle, add the beaten egg and begin to combine the mixture with floured hands. Work in the thyme leaves and continue until a smooth dough has formed. (Be careful not to overwork it or the dough will end up too dense and won’t expand when it goes into the water.)
- Cut the dough in half and shape each piece into a long cigar shape about 1.5cm thick. Using the back of a floured table knife, cut each length of dough into 2cm pieces to make ‘pillows’ or individual gnocchi. Gently press each one in the centre using your floured finger. The dent will hold more sauce and allow the gnocchi to take on more flavour.
- Bring a large pan of water to the boil. Add the gnocchi, tilting the pan from side to side briefly to stop them sticking together, then simmer for about 1½–2 minutes until they start to float. Drain the gnocchi and leave them to steam-dry for 1–2 minutes.
- Meanwhile, start to make the sauce. Heat a frying pan over a medium-high heat and add a little olive oil. Add the gnocchi to the hot pan with a pinch of salt and black pepper and sauté for 1–2 minutes on each side until nicely coloured.
- Add the peas to the pan with a knob of butter and the thyme leaves. Toss to heat through, then add the lemon zest. Serve with grated Parmesan cheese.