Spring Vegetable Stew

Name: Spring Vegetable Stew
Ingredients: 1/4 pound thin white asparagus, cut into 1-inch lengths; 1 cup shelled fresh cranberry beans (4 ounces or 1 pound in the pod); 2 tablespoons extra-virgin olive oil; 20 thin scallions, white and pale green parts only; 1/4 pound Hon Shimeji or beech mushrooms (available at Asian or specialty food markets); Salt; 6 white turnips, about 2 inches in diameter, peeled and cut into wedges; 2 medium carrots, cut into 1-inch-long sticks; 2 1/4 cups vegetable stock; One 6-ounce zucchini, halved lengthwise and sliced crosswise 1/4 inch thick; 1/2 teaspoon finely grated lemon zest; 1 teaspoon fresh lemon juice; One romaine heart, cut into 2-inch pieces; 2 tablespoons crème fraîche; 1 tablespoon small chervil leaves; 1 tablespoon minced chives