Potato, Asparagus & Fennel Ragoût

Heat the oil over medium-high heat in a large saucepan or a small Dutch oven. Add the onion, along with a few pinches of salt and a few grinds of pepper. Cook, stirring frequently, until the onion softens and starts to turn golden, about 5 min. Add the asparagus, fennel, and potatoes to the pot, along with a few more pinches of salt and pepper. Cook, stirring, until the vegetables are well coated with oil and the asparagus has turned bright green, 2 to 3 min. Add the chicken broth, raise the heat to high, and cover the pot. When it comes to a boil, reduce the heat to medium and keep the broth at a lively simmer. Cook, covered, until the potatoes are tender, 7 to 10 min. Stir in the cream, mustard, dill or parsley, and a squeeze or two of lemon juice. Adjust the seasonings and serve.