Combine 1/4 cup all-purpose flour, 2 tablespoons unsalted butter, cut into 1-inch cubes, 2 tablespoons granulated sugar, and a pinch of kosher salt in a medium bowl. Use your fingertips to rub the butter into the dry ingredients until the mixture is well combined and crumbly, with both lima bean- and pea-sized clumps. Place in the refrigerator until ready to use.