Avgolemono is a soup. Or a thickish sauce sometimes thought to be a precursor to mayonnaise.
We had a recent thread on the soup, my post includes a link to the basic recipe I use, though I add carrots and use orzo instead of rice.
As to the sauce, I've only made it once long ago. This might be a place to start with the sauce but hopefully Koukouvagia or Nicko will be along soon to give better...