apple, sage, and caramelized onion grilled cheese

Cut the onion into half, then into long slices. Add 1 tbsp butter to a large pan or cast iron skillet over medium heat. When the butter melts, add the onion. Let the onion cook for 4-5 minutes, stirring occasionally.
When the onions start to stick to the pan or brown, add about 1 tbsp of water and continue to stir. This will deglaze the onions from the pan and add steam for the onions to continue to cook.
After a few more minutes, add another splash of water. Repeat this process until the onions are golden brown and caramelized. This should take about 15 minutes. Take onions off the heat.
In a small pan, add olive oil over medium heat. When the olive oil is warm, add sage leaves and carefully fry on each side. Remove onto a paper towel.
Core apple and slice into thin slices.
In a large pan, add remaining 1 tbsp of butter over medium-low heat. Add two slices of bread and top each with mozzarella cheese, caramelized onions, apple slices, and fried sage. Add remaining slices of bread to the top.
Let the sandwiches cook until golden brown on each side and the cheese is melted. Enjoy immediately with a drizzle of honey!