Method

• 1.
  For the mayonnaise, whisk egg yolk and mustards in a medium bowl to combine. Drizzle in oil 1 tsp at a time, whisking until you have a thick mayonnaise. This should take a couple of minutes and shouldn’t be rushed. Season to taste.

• 2.
  Place potatoes in a medium saucepan with water to cover. Bring to a boil over high heat. Reduce heat to medium and simmer 20 minutes or until tender.
• 3.
  If using, shell the fresh peas into a bowl. Bring a saucepan of water to the boil. Add the butter and when it melts add the peas. When they change colour to a brighter green (this will happen almost instantly), use a slotted spoon to scoop them into a bowl. Leave the water boiling.
• 4.
  Add the kale to the saucepan and let it cook for about 10 seconds, until it turns a deeper green. Use the slotted spoon to transfer the kale to a colander to drain. Repeat with the spinach. Pat the greens dry with paper towel.
• 5.
  Drain the potatoes and return to their pan to keep warm. Squeeze greens well to press out any excess liquid and chop.
• 6.
  To the potatoes, add herbs, peas and greens. Stir in as much of the mayonnaise as you like (it should only be a thin glaze), using a wooden spoon to mix it around. Some of the potatoes will break up and fall apart – that’s what you want.
• 7.
  Finely grate the lemon zest over the salad. Cut the lemon in half, squeeze in the juice and combine. Transfer to a platter and serve warm.