Preheat oven to 350 F. Lightly butter 2 baking sheets. Combine all ingredients except butter and water in large bowl of heavy-duty electric mixer. Using paddle attachment, cut in butter until mixture resembles coarse meal. Slowly pour in water, beating until dough just comes together. Turn out onto lightly floured surface and pat to 3/4-inch thickness. Cut into 2 1/2 inch squares using floured knife. Arrange on prepared sheets, spacing 1 inch apart. Bake until light brown, about 15 minutes. Serve immediately. (Dough can also be made by hand.)
