Its generally mild flavor and delectable textures make summer squash versatile.
Preheat oven to 350 degrees. Have ready a 1 1/2-quart baking dish. Slice off 1 inch crosswise from stem end of each squash; set aside. Using a melon baller, remove the flesh from squash, bottoms and tops, leaving 1/8-inch-thick shells. Coarsely chop the flesh; set aside. Place the squash bottoms and tops in a steamer, and steam until just tender, about 15 minutes. Remove from steamer; set on a wire rack, cut side down.
In a large skillet, heat olive oil over high heat. Add onions, garlic, and reserved chopped squash. Season with salt and pepper, and cook until tender, about 6 minutes. Remove from pan, and transfer to a medium bowl.
Make the filling: Return skillet to heat; add lamb, and cook, breaking up the meat with the back of a wooden spoon, until crumbly and lightly browned, about 5 minutes. Stir in wine, and cook until all the liquid is absorbed, about 1 minute. Transfer meat to the squash mixture, and add breadcrumbs, pine nuts, currants, feta, cumin, coriander, cinnamon, mint, and 3 tablespoons tomato sauce. Stir well to combine.
Stuff the squash to the rims with the meat mixture. Place the squash tops on top. Pour the remaining tomato sauce into the baking dish, and place the stuffed squash in the sauce. Bake until the squash are tender, about 30 minutes. Divide the sauce among the plates, place the squash on top, and serve.