Line a baking pan (9x9" baking pan for thicker bars, or 9x13" baking pan for thinner bars) with parchment paper hanging over two sides (spray the pan first with cooking spray to help the parchment stick).  This will make the bars easier to remove.

Place all of the ingredients in a large capacity food processor (minimum 8 cup) and process until it is fine and sticks together (about 2 minutes), stopping the processor and scraping down the sides a couple of times.

Transfer the mixture to the prepared baking pan and press the mixture down very firmly and evenly using the bottom of a glass cup.  Refrigerate for a minimum of 2 hours or overnight, remove the bars from the pan using the overhanging parchment as handles, place on a large cutting board and cut into the desired number of bars with a sharp knife.  Store at room temperature in a covered container for up to one week or in the freezer for up to 2 months.