Pureed fresh corn makes a lighter dressing than mayonnaise for this updated classic.
Cook macaroni in salted water until al dente. Drain, rinse, and oil lightly, and set aside. Cut tips off asparagus at an angle. Cut remaining tender part of asparagus into same-size pieces; blanch and drain. Plunge into ice water. Drain again and set aside.
Cook corn in salted water until tender, about 5 minutes. Rinse to cool.
In a blender, combine 1 cup of the corn along with lemon juice, vinegar, mustard, sugar, and salt and pepper to taste; blend until smooth. Slowly blend in oil. Add scallions and 1/4 cup of the chervil leaves. Adjust seasonings.
Toss together macaroni, asparagus, remaining corn and chervil, capers, and the dressing.