Which ingredient is primarily used for coating the wok when making Chow Mein?

The primary ingredient used for coating the wok when making Chow Mein is salad oil. Salad oil, which is a type of neutral oil, has a high smoke point, making it ideal for stir-frying at high temperatures. This is crucial for achieving the desired texture and flavor in Chow Mein, as it allows the ingredients to cook quickly while preventing them from sticking to the wok.

Using salad oil also ensures that the flavors of the vegetables and proteins shine through without being overpowered by the oil itself. It provides a light coating that helps in achieving even cooking and browning, which are important for the final taste and mouthfeel of the dish.

Other ingredients like butter or sesame oil may not be suitable for this purpose due to their lower smoke points or stronger flavors that could impact the overall dish. Vegetable stock is typically used for enhancing flavor in soups or stews but is not used for coating the wok in a stir-fry context. Thus, salad oil is the most appropriate choice for this cooking technique.