Heat the oven to 350 degrees. In the bowl of an electric mixer, combine the brown sugar, salt, vanilla and pecan pieces. Beat on low speed to incorporate the ingredients then drizzle in the egg whites. Increase the speed to medium-low and beat for 4 to 5 minutes, scraping down the sides of the bowl as needed.
Drop the dough in rounded tablespoons onto a parcment lined baking sheet. Press each ball of dough with the back of a spoon or your 3 middle fingers to form a cookie 3 ½ inches in diameter and about one-eighth-inch thick.
Bake 10 to 12 minutes, until the edges are lightly browned.
Remove from oven and immediately remove the cookies from the baking sheet to a cooling rack. The cookies will be quite soft but will firm up as they cool. Once cool on the first day they are rather crisp, but on the second day (if you can wait that long) they develop that marvelously chewy texture I so love about these cookies.
