Preheat oven to 375 F. In a small bowl, mix together melted butter and olive oil. Brush a small amount of the mixture on the bottom and sides of the baking dish.
3 Tablespoons butter, 3 Tablespoons olive oil
Add garlic salt, and black pepper to the remaining butter/oil mixture. If you are using the red pepper flakes, you can either add some now or sprinkle it on at the end before the dish goes into the oven.
1 Tablespoon garlic salt, 1/2 teaspoon black pepper
Wash the potatoes and pat dry with paper towels. We do not peel them for this dish. Do not slice yet.
4 pounds russet potatoes
Cut shallots into 1/2-inch thick slices.
1/2 large shallot
Cut the ends off of a potato. Using a mandoline, cut potatoes into very thin slices, about 1/8-inch. You don’t want them paper thin, but you don’t want them as thick as when you make potatoes au gratin.
Working with one potato at a time, place a stack of potato slices into the prepared baking dish. Once you have a couple potatoes in the dish it will become easier to stand them up. Keep stacking and tucking until the pan is full.
Tuck slices of shallot into different areas of the potatoes.
Brush melted butter mixture all over the potato slices until you have used it all.
Place baking dish onto a baking sheet. This is important to insulate the bottom of the baking dish and keep the potatoes from sticking to the bottom of the pan.
Place in oven and bake for 70 minutes.
Sprinkle the rosemary on top of the potatoes and place back into the oven for another 15-20 minutes. Top will be brown and crispy and the potatoes inside will be tender. Use a fork or skewer to test for doneness.
Russet potatoes are best for this dish because of their starchiness. This helps the potatoes stick together. We did not peel our potatoes for this dish. If you choose to do the same, be sure to wash and scrub the potatoes well. You can peel them if preferred!