In the heat of the current gelato-and-frozen-yogurt wars, you might not think there was room for another major frozen-dessert concept. But while Grom, Pinkberry, Yolato, and the rest compete in Manhattan, Öko, a greener-than-green business serving two flavors of Greek-style frozen yogurt in a store in which nearly everything is biodegradable, has tailored itself for Park Slope. The walls and counter are made of compressed sunflower seeds; the spoons and straws, from potato starch. Even the plates, though seemingly made of transparent plastic, are actually composed of processed corn. The toppings are also all-natural, mostly fruit — blackberries, mango, kiwi pieces, and the like — along with dry toppings like shaved coconut, sliced almonds, dark-chocolate chips, and dried Turkish apricots. “This is just our first store,” general manager Mateo Braghieri tells us. “We want to open more.” Because, you know, there aren’t enough high-powered frozen-yogurt chains around.