Thistle salad

For 4 people:
500 gr of thistles
1 tablespoon mustard
1 bunch of parsley
1 lemon
2 tablespoons vinegar
4 tablespoons extra virgin olive oil 
salt and pepper to taste

Wash and clean the thistles; remove the ribs and cut them into pieces of about 15 cm long.
Boil in a pot with salted water, add 2 slices of lemon to prevent blackening.
As soon as they are cooked, remove them from the pan and dry them with a cloth.
Put in a bowl of olive oil, vinegar, a pinch of salt, some freshly ground pepper and mustard with a fork, mix well to form a smooth sauce.
Slice the coasts of thistle into strips and collect them into a salad bowl; sprinkle with the sauce previously prepared, mix well, sprinkle with chopped parsley and serve.