preheat skillet to 350°F

brush the butter on one side of each slice of bread and put it butter side down on a cutting board

split the cheese in half and spread it across each piece of bread

layer the chicken, then avocado on top of the cheese, then the mayonnaise

cover the sandwich and place it in the pan

put a plate or steak weight on top and let it sit for 2 minutes

check regularly to make sure the bread doesn't burn.

flip the bread and repeat

when the bread is nice and brown, check to see if the cheese has melted. Serve hot.