Roughly chop the beets and herbs. Add all to the food processor with the walnuts and garlic and process until you have a coarse paste.
Add the oil and vinegar and season generously with salt and freshly ground black pepper. Taste to check the seasoning, you may need to add a little more vinegar if the beets are particularly sweet. Set aside for the flavors to mingle while you make the pita chips.
For the Pita Chips
Separate each pita into two pieces and slice each into 2-3 strips diagonally.
Arrange on baking sheets, brush with the oil and season with salt and freshly ground black pepper. Bake in the oven for 10-15 minutes or until the pita chips are dry and crispy.
The chips will keep in an airtight container fora week.