The most popular type of bingsu in Korea is pat-bingsu.  It is made by adding to ice flakes a paste called dan-pat(sweet red bean)_a mixture of steamed red beans(adzuki beans) with sugar and salt.  Over tiem, as more and more bakeries and coffee shops started selling bingsu and other ice-based desserts.  It's now enjoyed not only in the hot summer but all year round.