The mixed heat method occurs when you cook using by a dry and moist method. The most popular types of cooking methods that are mixed heat are braising, stewing, and making a pot roast. Additionally, this method can be used on a variety of ingredients, such as vegetables and even desserts, but it is most commonly used on meat.
Some small reminders:
Dry cooking occurs when food is exposed to a high amount of temperature without any moisture being created. This often occurs in a pan without a lid or in the oven.
The moist method occurs when water, broth, or juices are used to add moisture to the cooking process. This is often used to soften foods.
Hope this helps!