Shikaku-mame 四角豆、literally square beans, are also called winged beans. Shikaku-mame is a crisp green bean with slightly bitter notes that can be blanched, sautéed, or fried as tempura. I came across a package at Tsukiji Market for 100 JPY ($1 USD). I asked the shopkeeper her suggestions for cooking and she suggested ohitashi-style and sautéed.
Rinse the shikaku-mame in water and pat dry. To sauté, simply panfry with a small amount of oil and season with salt and pepper. This version was a bit bland. I will try this once more, but with some pork and other vegetables.
The ohitashi-style was my favorite. Blanch in hot water and shock in ice water. Cut into bite-size pieces and season with soy sauce and katsuobushi. In the photo above we used katsuo-kona, a powder made from smoked bonito flakes. The beans are crispy and have a pleasant hint of bitterness.
Peak season: September and October
Scientific name: Psophocarpus tetragonolobus
Kitazawa Seed Co. link