It's important to monitor the heat of the skillet carefully while cooking these sandwiches. The goal is to cook them long enough for the cheese to melt and the sandwich to heat all the way through without burning the outside of the bread. If cooking sandwiches in a skillet, simply turn the heat down to medium-low if it appears that the outside is cooking too fast. If you're using a Blackstone Griddle and it looks like the outside of the sandwiches are beginning to burn before the cheese is melted, move the sandwiches to the outside of the cooktop and turn the burner heat down slightly. Another trick is to flip the sandwiches from side to side several times while they cook. Flipping the sandwiches every minute or so can keep the outside from burning while allowing plenty of time for the cheese to melt.