I made this for supper club last weekend (theme was Mexican, loosely), and this was stupendous. First, if it is hot where you are (and it is sure hot where I am), this is a perfect appetizer. We all thought our body temperatures cooled off several degrees just eating. It is also tastes so, so good. My goodness. This recipe comes from Jody Adams, from the "In the Hands of a Chef" cookbook. This is also a two day recipe, perfect for when you are hosting a summer supper (you make most of it ahead, and just do assembly and cutting of the avocado right before). I am writing this as I made it, and I doubled it; it goes without saying you could easily halve this. I also make my own creme fraiche, and here is how I do it: I mix one cup of whipping cream with 2 tbsp of buttermilk, and put in a jar with a lid. I do this one day before I want to use it. I let it sit out over night and then refrigerate it the next morning - and then I use it later in the day (they say it will stay good for 10 days).