Chop pecans - you want a mixture of finely chopped and very finely chopped. I like to do this by hand, but if you want to use a food processor just divide the pecans in half, processing one half very fine and the other half not as fine.
Whisk together flour, pecans and salt.
Cream butter and sugar together until light and fluffy, about 2 minutes.
Add vanilla and mix well.
Mix in flour mixture until just combined. The dough will be very crumbly but hold together when pressed.
Use a tablespoon measure to form rounded balls. If you want the dough to be a crescent shape, place the ball of dough on the cookie sheet and gently form it into a crescent.
Bake at 325 degrees F for 18-20 minutes, the dough should be light and dry and just starting to brown on the bottom.
Cool for 30 minutes and then toss in powdered sugar.
I find the easiest way to do this is to gently place cookies in a gallon size bag, add the powdered sugar, and gently move the bag around until all the cookies are coated.