Fro-yo is a way of life. You either get it or you don't. For some, closing an evening by swirling low-fat yogurt into a cup and accessorizing it with myriad toppings is the happiest of endings. Mimi offers that treat in North Beach. The flavors rotate frequently, but salted caramel and Tahitian vanilla are regulars. Sample some of the more exotic varieties, especially green tea, taro, and watermelon sorbet. You pay by the pound, so try to sail under the $5 mark on the scale. Toppings such as fresh fruit, cookies, and chocolate chips can really add up, but the soft mochi and burst-in-your-mouth fruit-flavored boba balls are light enough to keep the weight in check.