At its best, pesto is fresh, green, and full of herbal flavor. Could it stay that way even when added to an American pasta salad?
Most pasta salads made with pesto are unappetizing once allowed to sit for a bit. The pesto's bright green color dulls, its flavor fades, and its texture turns greasy and clumpy.
Pesto should be light and refreshing. We wanted the same qualities in a pasta salad made with pesto.
The basil in the pesto presented our first problem, turning dark and muddy after a few hours. Adding another green element--fresh baby spinach--provided a bright green color and smooth texture without interfering with the basil flavor. We found we needed to thicken the texture of traditional pesto; a moderate amount of mayonnaise served as a perfect binder, keeping our pesto creamy and luscious. Timing was also an issue; when we added the pesto to hot pasta, the pasta "cooked" the basil, deadening its impact. The solution was to let the pasta cool in a single layer on a rimmed baking sheet, tossing in a splash of oil to prevent sticking, before we added our sauce. We finished our salad with some flavor tweaks: lemon juice, extra toasted pine nuts, and cherry tomatoes.