Preheat oven to 300 degrees F.
Cream butter until light and fluffy.
Slowly add sugar and pine needles, scraping down sides.
Mix flour and salt together. Add all at once to the butter/sugar mixture, and mix just until incorporated. Do not over-mix.
Refrigerate dough for 30 min to cool, this will make it easier to work with
At this point you can either use a rolling pin and roll to about 1/2" thick to cut with a cookie cutter or. you can also just roll the dough into small balls and press them flat on the cookie sheet to bake - that's usually what we do.
Bake at 300 degrees F. for about 20-25 minutes, until pale and barely golden. Check at 18-20 minutes.
Remove from oven and sprinkle with pine sugar if desired. Allow to cool on cookie sheet for 5 minutes before removing to a wire rack to finish cooling.
Store shortbread in an air-tight container for up to 2 weeks.
Put 2 Tablespoons sugar in food processor or strong blender (I use a Blendtec) with 2 teaspoons chopped pine needles. Pulse until needles are finely chopped.