Preheat oven to 325F.

Pulse pecans in a food processor a few times until they are fairly finely chopped. Pour out half the nuts into a large bowl and then continue processing the rest until they are the texture of cornmeal, 20 seconds. Pour out the rest of the nuts into the bowl. Add flour, salt, and cornstarch to the bowl and mix well.

With a hand mixer or with a stand mixer using the flat beater, beat the butter until fluffy. Add the sugar and continue beating until light and smooth, about 2 minutes. Add the vanilla and beat it in, scraping down the sides of the bowl with a rubber spatula as needed.

Pour in the flour and pecan mixture and beat on low until almost all the flour is mixed in. Then shut off the mixer and mix in the last bits by hand with the spatula. You should have a smooth dough with no uncombined flour. If it's still a little shaggy, give it another turn or two with the spatula.

To measure out the cookies I highly recommend using a #100 cookie scoop. It holds 2 teaspoons and makes the work fly by, as well as giving exactly even amounts. Just scoop out the dough, filling the scoop evenly, and release it onto the cookie sheet. Alternatively, measure out 2 teaspoons of dough at a time, roll it in your hands until it's round and arrange the cookies onto the cookie sheet.

Bake cookies for 13 minutes. When done, remove the cookies to a cooling rack and allow to cool to room temperature.

Once the cookies are fully cooled, roll them in confectioners' sugar and arrange them on a plate.