Parging over tar?

I have a walkout basement and have parging on my above grade exterior concrete block walls.   In a small area I have dug out a couple of feet to add a patio near my basement walk-out door.   The problem is that the area of the wall that used to be below grade is covered with waterproofing tar.   I would like to continue the parging down over the tar to cover it up.   Is it possible to put parging over the tar?  Will it stick given that the moisture from the mortar mix won't be able to be absorbed into the concrete block since it is now covered by tar?  Can I remove the tar?  If so, how?  Any other suggestions? 

thanks,

Bantam