I want to make a particular onigiri that I had at an asian restaurant. It is basically filled with peanut butter and covered with sesame seeds. So far, simple enough. However, the ball is topped with a blob of peanut butter and then a spot of a white sauce.
My question, assuming this kind of rice ball is common, is what is that white sauce on top meant to be? It didn't taste particularly sweet, nor vinegary, so I want to discard cream, mayo, salad cream, sour cream and ali-oli. But what else could it be?
Thanks in advance :)