Im no expert in cooking magick so dont take my word as defenant.
The resipie Shouldnt affect the actual spell rather it be the energy placed in it to be the actual working. Energy is bound in the food passively from just making it. And then too you can add more to set it to work certian needs.
Blessing of the herbs I dont belieave is nessisary but it sure could help. I think your best means of blessing it would be using holy water, which you can make your self. Mrsfendishbat on YouTube has a good resipie for holy water along with other good tutorials on kitchen magick.
And as to the actual cookies you could simply Google for a simple sugar free recipe. And for good karma and health use organic ingredients c:
Hoped it helped a tad.