Photograph: Dan Jones
Bring a pan of salted water to the boil and simmer the leeks for 90 seconds. Drain, rinse in cold water and pat dry.
In a large bowl, whisk together the vinegar, oil and mustard, lightly season and set aside.
Get a griddle pan hot with a dab of oil and griddle the leeks for a minute or so on each side, until nicely charred. Toss them in the vinaigrette; set aside. Fry the breadcrumbs until golden, then stir through the herbs with a pinch of salt. Arrange the leeks on the plates, crumble over the cheese, drizzle over the remaining vinaigrette and scatter with the breadcrumbs.
Kitchen secret: griddling leeks gives them a lovely smoky sweetness. This recipe works well with asparagus, too. Serve with crusty bread.