How to Make It
Pulse the flour and salt in a food processor until combined. Add the butter and pulse until the mixture resembles coarse meal with a few pea-size clumps of butter remaining. Add the Parmesan and pulse until dough comes together.
Form the dough into two 12-by-1 1/2-inch logs. Wrap tightly in plastic wrap and refrigerate until firm, about 2 hours or up to 2 days.
Heat oven to 350° F. Line 2 baking sheets with parchment.
Cut the logs into 3/8-inch slices. Place the cookies 1 inch apart on the baking sheets. Bake, rotating the sheets halfway through, until the cookies are golden brown around the edges, 12 to 14 minutes. Let cool slightly on the baking sheets, then transfer to a wire rack to cool completely.
Tip: Use the best-quality Parmesan you can, preferably Parmigiano-Reggiano.