Using stabilizers, slice ⅛" slits in the potatoes without cutting all the way through.
Once the potatoes are all sliced, fan them out and sprinkle with salt and pepper between the slices.
Spoon or baste the melted butter between each layer of the sliced potatoes.
Bake for 55-60 minutes.
Place a slice of the cheddar cheese squares between each layer of potato.
Sprinkle grated Parmesan cheese over the potatoes and return to the oven for an additional 10 minutes bake time.
Bake for an additional 10 minutes or until cheese is melted.
Top with chives and serve hot.
Notes
Tips:
Sharp knife — Thin cuts using a very sharp knife are what create the crispy edges.
Even cuts — slice as evenly as possible so each layer is perfectly tender. We used a ruler to make marks across the top at ⅛-inch intervals before slicing through.
Stabilizers — we used chopsticks but kitchen knives and wooden spoons are also great. Place one on each side of the potato so as you're slicing, the knife will stop on the item before slicing the potato through. Adjust as you go since they all taper.
Potatoes — uniformly shaped russet potatoes are need for this recipe. Find those that are all long and skinny or round and fat. This will allow for even cooking time. Thicker potatoes will require additional cooking time.
Cheese — Using cheese slices makes for quick work, but we found not cutting them into perfect squares was best. We make some larger for the center/thicker parts of the potato and smaller for the ends.
Seasoning — as the starches release during cutting, it will cause the layers to stick together. While fanning them out/apart, add the salt and pepper.
Cast-iron skillet — a cast-iron skillet is always the best option for everything but especially when cooking this recipe, as it retains and distributes the heat evenly for the perfect potato.
Toppings — sour cream, queso, and salsa are all excellent toppings or dips.