The process generally involves infusing cannabis into butter (called cannabutter), which is then mixed into a standard brownie batter. First, you'll decarb the cannabis by baking it, then simmer it in butter to extract the THC. Once infused, the cannabutter is used as a substitute for regular butter in your brownie recipe. https://www.dcleafly.com/post/how-to-make-pot-brownies-a-step-by-step-guide