By Ali Slagle — This weeknight meal is silky, slurpable and so quick to pull off. It follows the tradition of wafu or Japanese-style pasta, and combines brown butter, udon and spinach, but the classic combination of savory sauce, chewy noodle and green vegetable allows plenty of room for improvisation. Instead of soy sauce, you can add umami with Parmesan, miso, seaweed or mushrooms. Instead of black pepper for heat, grab ginger or chile flakes, oil or paste. For more protein, boil eggs or shelled edamame in the water before the udon, or add tinned mackerel or fresh yuba along with the sesame seeds. Udon noodles, found fresh, frozen or shelf-stable, are singularly bouncy and thick; if you can’t find them, use the thinner, dried style that resembles linguine.