the more the better is quite good, but if there's too much:
1) your cake won't hold together
2) thcdissolves in butter, as moojum says, it's easier to make them from cannabutter.

to make cannabutter : fill a big saucepan with water, make it boil, set 250 gr of butter in the boiling water, set your weed into the saucepan, cover.... and come back 30 minutes later... (!!!neigbourhood warning, it SMELLS really hard !!!).

when that's done, stop the heating let boil down... take a siringe and carefully collect the butter floating on top of the water. set u'r butter in a plate and in the fridge, let it cool .. here you have your butter.

This butter is what world known french writer Charles Beaudelaire used to eat daily and called his "green marmelade".

To come back to your cookies, just replace the butter of your pack with the cannabutter and make them as usually... !!! change the receipts temperature and time, the oven's temperature may not exceed 100°Celsius (212° fahrenheit).

Hope it helped...