Trim ends of 2 pounds fresh patty pan or other summer squash. Scrub and shred coarsely using the largest holes of your grater (you should have about 8 cups). Using a 10-inch or larger frying pan with a tight-fitting lid, combine 4 tablespoons (1/8 pound) butter, 2 tablespoons water, 1/8 teaspoon pepper, 1/2 teaspoon salt, 1/2 teaspoon basil leaves, and 1 small clove garlic, minced or mashed.
Place on high heat, mix in the squash, cover, and cook until the squash is just tender, about 5 minutes. Take cover off the last minute or two, if necessary, to evaporated most of the liquid.
Meanwhile, mix 1 cup sour cream with 1 tablespoon flour until smooth; stir into squash. Bring to a boil, stirring until smooth.