We made one of our favorite cookie recipes, punitions, which are French shortbread cookies. The recipe calls for salted butter, an ingredient sparsely used in the test kitchen. However, for this recipe it is a necessity. I assumed it was strictly for flavor with the salt balancing out the sugar in the dough. After some research, we found another benefit of using salted butter in shortbreads. The salt tightens the proteins in the dough, helping to make it chewier. We love a good scientific explanation for baking techniques, almost as much as we love these cookies.