Step 1Trim artichokes according to preparation instructions and cut them into sixths. Remove chokes with paring knife. Set artichokes in bowl with enough water to cover and lemon juice.
Step 2Melt butter in wide soup pot over medium-high heat. Add shallots and leeks and cook, stirring frequently, without browning, 3 to 4 minutes. Add wine, raise heat and simmer 2 minutes.
Step 3Drain artichokes and add them to pot along with fennel and broth. Season with 1 teaspoon salt and pepper to taste, then press a piece of crumbled parchment or wax paper directly over vegetables. Bring to boil, then simmer, covered, until artichokes are tender, about 35 minutes.
Step 4Meanwhile steam potatoes until tender, 12 to 15 minutes.
Step 5When artichokes and fennel are tender, remove them with slotted spoon to dish. Whisk creme frai^che and mustard into broth and boil briskly to make a thin sauce, 5 to 10 minutes. Add peas, cook over medium heat until tender, 3 to 4 minutes, then return vegetables and potatoes to pot. Add fennel greens and serve.
As the season progresses, take advantage of small market carrots, the last asparagus, the first zucchini or tender new turnips. For the fall artichoke crop, include diced celery root with the artichokes. Cool-weather sorrel, finely chopped (about 1/2 cup per recipe) simmered with the cream and then pureed, adds a bright, lemony bit to the dish.