Method

• 1.
  For the pesto, place 50g peas and all remaining ingredients in a blender and whiz until smooth (do not over-whiz or it will turn brown). If making in advance and refrigerating, make sure it’s at room temperature when ready to serve (colour will change slightly).
• 2.
  To make the gnocchi, place the potatoes in a medium saucepan and fill with cold water. Bring to the boil and simmer until potatoes are fully cooked but not falling apart (about 20-25 minutes). Drain and return to pan over low heat to remove excess moisture. While potatoes are still hot, peel and discard skins. Pass potatoes through a ricer onto a floured bench (make sure there are no lumps).
• 3.
  Make a well in the centre of potatoes and add yolk, nutmeg and a pinch of salt flakes. Sprinkle generously with flour and, using a fork, work into potato (amount of flour required will depend on how moist potatoes are; start with three-quarters of the flour), but do not over-work.
• 4.
  Very lightly dust a work surface with extra flour. Divide the dough into 4 portions. Roll each portion into a 2.5cm-wide log and cut into 2.5cm pieces. Using a fork lightly dusted with flour, press down on each gnocchi piece.
• 5.
  Bring a large saucepan of salted water to the boil over high heat. Cook gnocchi, in batches, for 1 minute or until they start to rise to the surface. Strain and divide among bowls, reserving 2 tbs cooking water.
• 6.
  Stir reserved cooking water into pesto. Spoon over gnocchi. Top with remaining 100g peas, chopped walnuts and extra Parmigiano to serve.