Sitaw (Long Bean) Leaves
[Talbos ng Sitaw (Philippine); Vigna unguiculata var sesquipedalis]
Filipino home cooking has a long tradition of using a wide assortment of greens, usually harvested from the back yard garden. Some of these are not familiar to our North American kitchens, and this is one of that sort. It can be used in stir fries and soups.
Note that the word "Sitaw" in Filipino is inexact. It is used both for the Asian long bean and for the more recently acquired Green Bean, brought by Europeans (who got them from Mexico). Presumably your supplier is providing the right kind.
More on Beans, Peas and Lentils.
Buying: These can be had from large and active Philippine markets. My local market puts out bundles of greens on Friday or Saturday morning for sale over the weekend. Don't depend on the signs - the bundles may be all mixed up (they expect their customers to know what they are). Note the lack of fuzz and the lack of binding tendrils (these plants are "bines", climbing by twisting around stuff). Squash leaves are very fuzzy and Chayote leaves have lots of binding tendrils. Bitter Melon leaves are much smaller and Chili leaves have a simple elongated shape.
Leaves should be fresh looking, dark green, without black spots and not wilted. If it needs refreshing when you get it home, cut off the bottom 1/2 inch of the stems and use the "full immersion" method in cold water to refresh them, for about 1/2 hour. Then spin off the water in your salad spinner.
Storing: These are fairly sturdy and will last up to 5 days loosely wrapped in the fridge, if they are in good shape to start with.
Preparing: Pull off the leaves, leaving the leaf stems behind (they're tougher than the main stems). Tear them to the size you want. You can use any flower buds you find, and the tender tips - but only so far as you can pinch them off with a snap, with no hint of fibers. Fibrous stems will be too stringy to eat and will not become tender even with extended cooking.
Cooking: These are pretty sturdy greens and can stand at least 20 minutes simmering and still be quite firm.