Preheat the oven to 350 degrees. Butter a large cookie sheet.
In a food processor fitted with the steel blade, pulse the pecans until they are finely chopped. Add the powdered sugar, flour and salt, and pulse again. Scrape down the sides of the bowl with a spatula if necessary.
Drop in the butter and shortening chunks, and pulse a couple of times. Add the egg and pulse again, just until the mixture starts to come together. Roll the dough into 1- to 1 1/2″ balls with your hands.
Place the balls on the baking sheet, spacing them 1″ apart; give them a light pat on the top. Bake until the cookies are golden brown, about 15 minutes. You may need to bake two batches.
Generously, really super generously, dust extra confectioners’ sugar over the top of the cookies.