How to Make It
In a medium bowl, using an electric mixer, beat the butter with the tahini, confectioners' sugar and salt at medium speed until smooth, about 3 minutes. Add the flour and beat until incorporated. Turn the dough out onto a work surface and knead just until it comes together. Divide the dough in half and roll each piece into a 15-inch log, about 1 inch thick. Scatter the sesame seeds on a sheet of parchment paper and roll the logs until completely coated. Roll each log in parchment and refrigerate until chilled, at least 1 hour.
Preheat the oven to 325° and line 2 large baking sheets with parchment paper. Unroll one log and slice it 1/4 inch thick. Arrange the slices on the baking sheets. Bake the cookies in the center and lower-thirds of the oven for about 25 minutes, or until golden, shifting the pans from front to back and top to bottom halfway through baking. Slide the parchment onto a rack and let the cookies cool completely. Repeat with the second log of dough.