I've been going to the exact same fruit'n'veg stall at the markets since forever. A scavenge and a scrounge recently unearthed the fact that they don't stock watercress! Disaster. My balcony used to be my sole supplier of watercress for my many salads, soups and sandwiches cravings... in fact, I need to get my Dadsy's Chinese Watercress Soup, that reminds me...
Anyway, a walk across the way and I suddenly discovered the neighbouring stall, previously overlooked, has watercress in abundance! At only 1.99 per large box!
If you've never used watercress before, it's a peppery, crunchy treat raw in salads and sandwiches - in particular the tender baby leaves; or a beautiful, tender treat in soups and stews with a milder, robust "Chinese vegie" nommage to its stems and base leaves.
The markets that day had the most luscious looking rare roast beef I've ever seen just down "meat alley" as the other half calls it, as well as the standard olive bread, so here's what became of that (slathered with Philly cream cheese):

My all-time favourite is smoked trout, watercress, boiled potato & goat cheese salad. Here was my first attempt, well before the great balcony aphid plague of 2010:

Let me know if you have any other inspired watercress recipes!