Coat inside of 10" cast iron skillet with 1 tablespoon of the butter. Add half of the potatoes, spreading them out in an even layer. Drizzle the water over potatoes.
Dot 3 tablespoons of butter across the potatoes. Sprinkle with salt and pepper, as desired. Add about 2/3 of the onion and then 2/3 of the bacon. Sprinkle on half of the herbs.
Then add 1-1/2 cups of the 6 Cheese Italian and 1 cup of the Cheddar.
Now add the remaining potatoes and dot with the remaining 3 tablespoons of butter. Sprinkle with salt and pepper. Add the remaining onion, bacon, and herbs. Sprinkle the remaining 6 Cheese Italian over the top, finishing with the remaining Cheddar.
Poke a few pieces of the bacon up through the cheese, for a pretty effect, if desired. Cover skillet loosely with foil, taking care to not let the foil touch the top of the potatoes (so the cheese doesn't stick to the foil).
Set skillet on hot grill grates and check the potatoes after they have been on the grill for 30 minutes, adjusting temperature if needed. The pan should be sizzling, but make sure the temperature isn't too hot that the potatoes are burning.
Let cook for about 50 to 60 minutes total, or until potatoes are very tender.
Remove foil and let cook for a few minutes more to brown up the cheese, if desired.
Remove skillet from heat and let sit for a few minutes before serving. Sprinkle with additional black pepper and chopped herbs, if desired.