Line an 8 x 8 inch or 9 x 9 inch cake pan with parchment paper. Allow the paper to hang over the sides for easy removal. Sift the dry ingredients into a large mixing bowl until there are no lumps. Stir in the vanilla and melted butter until all the dry ingredients are moist.
Use fingers and massage the ingredients together until the dry ingredients are fully moistened and the mixture is crumbly. Pour mixture into the prepared cake pan. Use hands or back of a measuring cup and press the mixture firmly throughout the cake pan.
Spread a light layer of frosting evenly over the slab then cut the slab in half. Freeze for 1 hour or until firm. Remove from the freezer. Grasp the overhanging parchment paper and carefully lift the slab out of the pan.
Place the portions on top of each other. Cut the slab into the desired size pieces. Use immediately or store loosely in an airtight container in the freezer up to 3 month. Do not pack the pieces tightly. You do not want to turn them into crumbs.
Notes
This recipe yields about 1 1/2 TBS of pieces. The nutritional value is based on about 2 TBS of pieces.