Koosa (or kousa, cousa, coosa) is a light green, smaller-sized Lebanese summer squash, also known as tatume here in Michigan at our Meijer grocery store. If you can't find koosa, use zucchini or yellow squash, both delicious. Just be sure to cut the neck low enough to create an opening large enough to insert corer. Use either a meat or vegetarian filling for the koosa. Watch my video on koosa-making here. Get an heirloom quality koosa corer here, at MaureenAboodMarket.com.
Trim the koosa by cutting the stem end off, and if your squash is bent at the neck, cut below the bend. Shave off the dark point at the other end of the koosa.
Insert the corer in ¾ of the length of the squash and twist. Pull out the core. Do this a few times, scraping against the edge of the squash with gentle pressure until the squash is hollowed, leaving about 1/4-inch of koosa all the way around and taking care not to puncture the squash. If you do puncture a squash, it’s still useable. Just serve that one, the ugly duckling, to yourself and no one will know....
Fill each koosa with the stuffing, making sure the entire koosa is filled, but not packing the filling in too tightly. Fill only to about 1/4- to 1/2-inch depth at the opening of the koosa, leaving room for the filling to expand without pushing out of the koosa. You may have leftover meat stuffing that you can form into meatballs to be cooked with the koosa.
In a medium saucepan, par-cook the koosa (this is to avoid over-cooking the yogurt sauce by reducing the cook-time in the yogurt). Cover the koosa with water and bring to a boil. Reduce the heat and simmer for 15 minutes.
In another large heavy saucepan, begin to warm the laban over medium heat. In a small bowl, dissolve the cornstarch in the cold water. Whisk the cornstarch mixture into the yogurt, along with the crushed dried mint, and lemon juice. Taste and season with salt as needed.
Carefully transfer the par-cooked koosa from the poaching water to the pot of yogurt sauce, using a big slotted spoon (to leave behind as much water as possible).
Simmer the koosa in the yogurt for another 15 minutes, or until cooked through.
Serve the koosa immediately in bowls with yogurt sauce ladled over them, and finished with another dusting of dried mint salt.