Mushroom julienne is a dish made with sautéed mushrooms (preferably, wild) combined with sour cream or béchamel sauce and baked in small individual ramekins or cocottes under a cheese crust. It's one of those treats, eating of which is always accompanied by joyful moaning and multiple "OMG" exclamations. No exaggeration here!
Julienne is quite rich, so a small serving is enough to enjoy it. It’s served as a hot appetizer and I prefer to eat it with a teaspoon.