Place medium-sized non-stick skillet over medium heat then allow it to heat. Spread 1½ tsp unsalted butter on 1 side of each bread slice then place 2 pieces in the skillet butter side down. If your skillet’s large enough, you can add 4 pieces of bread, making 2 sandwiches at a time.
Immediately top each slice of bread with 1½ oz of sliced or shredded mozzarella—3 oz per sandwich. Cover skillet, but keep the lid slightly open—doing so will trap heat inside the skillet and help melt the cheese. When the bread is golden brown on the bottom and the cheese is melted—about 2–3 minutes in the skillet—remove bread from the skillet.
Place the sliced tomato and avocado on one side then season lightly with salt and pepper.
Place the other slice of bread on top and press lightly. Repeat for remaining sandwich. Enjoy!
One Last Thing
The key to a great color and crunch is to use moderate heat. This allows the butter and bread to crisp and color slowly for the ultimate satisfactory results!