I don't know how the cannabutter would react to the long and high baking times, my suggestion is to follow a regular recipe and brush on the cannabutter as it enters the last part of cooling on your cookiesheet. Not sure of the specifics but you can look it up, you'll need a candy thermometer fer this one. Just as you do your final fold on your toffe, temp your candy and when it gets a safe temp so the thc wont evaporate start brushing, you can look up cannabutter temps in this section. Your looking to get at least two layers of butter like a thin film. As the candy dries it will soak the cannautter in and your second thin layer should go on right before it solidifies, still warm and a little workable but almost solid. This should dry into the epidermal crust of your toffe. Hope this help and say hello to goofy fer me!