Wash but don’t peel the carrots and leave a tiny green tuft at the stalk.
Half-fill a small saucepan with water and bring to the boil.Add the beans and cook for 2–3 minutes until tender. Remove with a slotted spoon to a colander, cool under running water and then peel. Cook the carrots in the boiling water for 4 minutes until just tender. Drain and rinse under running water until cold. Peel the beans and carrots in a salad bowl.
Remove the leaves from the radishes, adding the good leaves to the salad bowl and discarding the damaged ones. Cut all but the tiniest radishes in half and chuck them all in. Pod the peas and put them uncooked into the bowl. Strip the mint leaves from their stalks, tear and add them to the bowl, along with the torn lemon balm, if using. Snip the chives in half, chop the picked parsley leaves and scatter both over the salad. Wash and roughly tear the lettuce leaves, then add to the bowl.
To make the vinaigrette, whisk the vinegar, mustard, sugar and salt in a bowl until smooth. Gradually whisk in the oils until the dressing becomes thickened, glossy and emulsified. Season with more salt, if necessary, and a couple of twists of black pepper.
Spoon some dressing over the salad and toss together well. Joy!