Raw cowpeas contain toxin components such as saponins and phytoalexins, which need to be heated so that the beans are cooked through in order to destroy their toxins. If cowpeas are not cooked through, people may be poisoned if they eat them. It is easy to stir-fry cowpeas unevenly resulting in toxin residues, so to ensure food safety, it is recommended to blanch them before stir-frying.
Blanching destroys the toxins and ensures that the fried cowpeas are safe to eat. However, if the portion is small, the stir-fry is even and you ensure that the cowpeas are well cooked, you can also just stir-fry them and eat them. In short, blanching before stir-frying cowpeas is recommended for safety.