In European kitchens, this dough is memorized by most cooks. They use it when they need a sweet, crumbly butter dough for cookies or tarts. In the metric system, it’s easy to recall. In fact, some people call it “3-2-1 dough” because it consists of three parts flour, two parts butter, and one part sugar (here, 300, 200, and 100 grams) with an egg or a bit of water to hold it together. Be sure to keep the butter cool while working it into the flour. If it softens (Viennese call this “burning the butter”), the crust will not be crisp.