Preheat the oven to 500 degrees F.
Spread a thin layer of salted butter on the outside of each piece of sourdough bread. Place a single layer of cheddar
on the inside of the sourdough bread
. Be sure to cover the full inside of the bread. Place a single layer of havarti on top of the cheddar, and be sure to cover the layer of cheddar. Place a single layer of Monterey jack on top of the havarti, and be sure to cover the layer of havarti. Place the other piece of buttered bread (butter-side out) on top of the Monterey jack to close the sandwich.
Carefully, place the sandwich on the hot sheet pan or tray. Place the sheet pan
or tray into the heated oven. Cook for 45 to 60 seconds, until the top slice of bread achieves golden-brown toasting.
Remove the sheet pan with sandwich and flip the sandwich. Place the sheet pan back in the oven. Cook for another 30 to 34 seconds, until the top slice of bread achieves golden-brown toasting and all cheese is fully melted.
Remove from the oven. Eat and enjoy!