OK, this may sound like an exotic or hard to get main ingredient--but its actually probably growing in your yard! If you've never tried chickweed, youve GOT to try it. its a mild, tender green, and it just tastes, well, GREEN. it also grows abundantly and spreads. harvest it by taking the vibrant green tips, the first few inches or so. it will grow back in a few days. apparently it also grows through the winter in some climates. you dont want the mouse-eared, hairy chickweed, you want the one with smooth leaves that can be identified by holding it up to light and you will see a row of hairs running up the side, that changes sides at each leaf junction.
Anyway, every time i make this, i end up practically licking the food processor. and there never any left to save. it is THAT good. and great to use while the traditional basil for pesto is out of season.