Mache, a delicate and tender green sometimes called lamb's lettuce, is available in better supermarkets. Watercress can be used instead.
In a small bowl, combine shallots and vinegar. Whisk in olive oil and add 1/2 teaspoon salt and 1/8 teaspoon pepper. Set aside to steep for at least 30 minutes.
Using your fingers, split the lava bean pods lengthwise and remove beans. Bring a medium saucepan of water to a boil and add 1 teaspoon of salt. Add beans and cook for 30 seconds. Remove with a slotted spoon or strainer, keeping water boiling, and transfer to an ice-water bath. When cool, lift out with a slotted spoon or strainer. Beel a bit of skin from a bean and pop the bean out by squeezing gently; repeat with the rest of the beans. Discard skins and set beans aside.
Trim and discard tough ends of asparagus and cut spears into 2-inch pieces. Add asparagus to boiling water and cook until tender but still firm, about 2 minutes. Drain and immediately transfer to the ice-water bath. Drain and set aside.
Combine fava beans, asparagus, endive, and mache or watercress in a large serving bowl. Season with remaining 1/2 teaspoon salt and 1/8 teaspoon pepper and drizzle dressing over greens. Toss well and serve.
10 ounces of mache, trimmed, can be replaced with 3 bunches of watercress, trimmed.