1 litre good quality fresh vegetable stock (see tip)
For the vinaigrette
1 tbsp dijon mustard
1 tbsp red wine vinegar
1 small shallot, very finely chopped
60ml extra-virgin olive oil
Squeeze lemon juice
For the pangrattato
Big glug extra-virgin olive oil
80g dried breadcrumbs
Finely grated zest 1 lemon
Small bunch fresh flatleaf parsley, finely chopped
Halve the leeks lengthways, then slice each length in half across the width. Rinse (see Know-how) and pat dry. Heat the butter in a large frying pan until melted and foaming, then add the leeks. Cook for 5 minutes, turning occasionally, until golden in patches. Add the stock and bring to the boil, then turn the heat down to a gentle simmer and cover the surface with a disc of baking paper (known as a cartouche). Poach the leeks for 20-25 minutes until very tender.
Meanwhile, combine the mustard and vinegar in a bowl or jug, then add the shallot and season well. Whisking continuously, drizzle in the 60ml oil to make a dressing. Add lemon juice to taste. Set aside.
For the pangrattato, heat a big glug of oil in a small frying pan. Add the breadcrumbs with some seasoning, then cook over a medium heat, stirring, until golden. Toss through the lemon zest and parsley.
Serve the leeks with a little of the stock, drizzled with the vinaigrette and sprinkled with the pangrattato.