This recipe for a vivid, vegetarian pasta sauce, made from blanched kale leaves and loaded with good olive oil and grated cheese, comes from Joshua McFadden, the chef at Ava Gene’s in Portland, Ore., and was inspired by Rose Gray and Ruth Rogers of The River Café in London The technique is absurdly simple and quick from start to finish, but the result is luxurious and near-creamy Feel free to play with the pasta shape, but no matter what you choose, be sure to let the blender run for a while at a powerful setting: You want the kale to completely break down into a smooth, bright, airy green puree.