Line a cookie sheet with parchment paper and spray it with cooking spray.
Slice all your potatoes into very thin slices. You can do this with a mandolin or a sharp knife. You should be able to see through your potato slices slightly when they are cut correctly. Discard the end pieces of the potato and try to keep your potato slices even. After you have your slices, place them into a bowl and cover with water, until you are ready to use them.
Now it is time to prepare your scalloped potatoes to bake. On your cookie sheet that has been lined with parchment paper and sprayed with cooking spray, sprinkle Italian-style cheese and parmesan cheese until you have a thick layer. Next, place your slices of potatoes in a row, starting at the end. Arrange your potatoes so that each one is overlapping the previous one by ½ width of the potato. The next row should overlap the first row and the current row. Once all potatoes are laid out, cover with Italian-style cheese and parmesan cheese. Bake at 350°F for 20-30 minutes, or until potatoes are completely baked.
While your potatoes are baking, prepare your filling. In a mixing bowl, combine sour cream and cheddar cheese. Mix in any seasonings desired, such as garlic, salt, pepper, and parsley. Chop green onions and prepare bacon bits.
Once your potatoes have been completely baked, remove them from the oven. Add a layer of the sour cream mixture, topped with bacon bits and green onions. Tip, make sure your layer of sour cream is thin, otherwise, it will cause your roll to collapse while baking a second time. Now that you have all your filling in place, it is time to roll your potatoes. To roll, pick up a corner of the parchment paper. Using your parchment paper to maneuver, start your potato roll, being careful to keep your parchment paper out of the actual potato roll. Roll it into a loaf shape and place it on new parchment paper.
Place your scalloped potato roll back in the oven for 5-10 minutes, or just until it is warmed through. Remove from the oven, and carefully transfer to a serving dish, using a spatula and the parchment paper to move. Top with slices of green onions and a dollop of sour cream if desired. Serve immediately and enjoy! Watch the video below to see how to make it!