Line a 8x8 or 9x9 square pan with wax or parchment paper.

Place all ingredients except walnuts and chocolate chips in a high-powered blender (such as a Blendtec) or food processor, and process until the mixture forms a thick mass.

Break up slightly with a spatula, add walnuts to the mixture, and pulse until the nuts are slightly chopped and distributed.

Break up the mixture one more time, add chocolate chips and pulse a few times to distribute the chips, or simply stir in the chips.

Press the mixture into the prepared pan. You can cover the top with more paper and press an equal sized pan to roll the top with a glass to flatten completely.

Place in freezer until firm, as this will allow you to slice them easier. Otherwise they are quite sticky. Slice into bars or squares and store the bars in the refrigerator.