Trim the stalks from the mushrooms and cut
each flat mushroom into thick slices. Leave the
chestnut and buttons whole if small, or halve if
large. Cook the beans in boiling salted water for
just a few mins so they stay crisp. Drain under
cold running water to quickly cool.
To make the dressing, blitz all of the ingredients
together in a food processor, adding an extra
teaspoon of mustard if you like. Season to taste
with salt and pepper. Pour the dressing into a
screw-top jar, giving it a good shake before using.
Season the mushrooms. heat the butter and
a drizzle of oil in a large frying pan. Add the
mushrooms and fry them over a high heat,
turning a few times. After a few mins, when the
mushrooms have taken on a roasted colour and
become tender, transfer them to a bowl. Shake
a little dressing on top of the mushrooms. Can
be prepared to this point up to 2 hours ahead.
Tear the Parma ham into pieces. Whisk the
mushroom juices into the rest of the dressing.
lay some of the lettuce leaves on a large
platter, then layer up the rest quite casually
with the mushrooms, Parma ham, eggs and
any extra herb sprigs.
Drizzle the dressing liberally over the salad