Squash blossoms are the ultimate in edible flowers. Unlike nasturtiums, borage, violets and other pretty posies consigned largely to salad and ice cube duty, squash blossoms can be stir-fried, frittata-ed, casseroled, gratineed and, most notably, stuffed. If you have loads of blossom go ahead and knock out successions of risottos, pizzas, frittatas and casseroles, where they …