That depends on what you make. If it's a thousand-layer pastry or egg tart skin in West Point, you need to use butter, because this kind of pastry directly wraps flaky butter in dough and repeatedly rolls and folds it. The butter is solid and won't flow out. If you are making Chinese shortcakes like granny cakes, you can use peanut oil. This kind of shortbread is not directly covered with oil, but with a layer of dough mixed with oil.