Made without any Bolognese or tomato sauce, a white lasagna is a celebration of pasta and vegetables bound together by a creamy béchamel. This version, brimming with herbs, spinach, asparagus and peas, is an ode to spring, like a baked pasta primavera in its richest form. Serve it in small squares as a first or pasta course, as it’s served in Italy, or in more substantial slabs as a meatless main course. It’s a bit of a project, so if you want to work ahead, you can make the béchamel up to a week in advance and store it in the refrigerator. The baked lasagna can also be made ahead and refrigerated for up to two days. Reheat, covered, in a 350-degree oven for 30 to 45 minutes.
