Cooking up a storm is a phrase that is often used to describe the act of cooking a large and impressive meal or being in the midst of a cooking frenzy. However, there are many antonyms to this phrase that indicate the opposite. One might say that they are not cooking up a storm if they are not cooking at all or if they are cooking very little. Another antonym could be cooking down, as in reducing the amount of cooking being done. Additionally, someone may simply state that they are not cooking a storm, indicating a lack of urgency or intensity in the process. All in all, antonyms for cooking up a storm include not cooking, cooking down, and not being intense or urgent in the process of cooking.