I've never had a green sauce - it may have been some wasabi and mayo - do you think there was any mashed avocado in there too? I would try mayo, a bit of wasabi, garlic (smooshed well), a bit of sesame oil, and mashed avocado. I certainly have never made it but it sounds like it might work. The avocado would give a nice creaminess to the sauce.
Also, when you make your spicy sauce give it time for the flavors to blend. Make it a day ahead or so. It really helps - otherwise it tastes too much like mayo in the beginning.
"Count yourself...you ain't so many" - quote from Buck's Daddy