Mix peanut butter, syrup and vegan sugar. Warm till fairly runny, do not boil. Stir in flax and vanilla. Pour mixture over cereal and mix. Press into oiled 9x13 pan. I used Earth Balance spread to oil the pan, and to help press the mixture down.
Definitely not low calorie, but a great way to get the kids to eat their flax. I did not use natural peanut butter, but I think I will try it next time as they are sweet.