Preheat the oven to 425 degrees and heavily grease a large baking sheet.
Slice the potatoes as thinly as possible. In a large bowl, toss the potatoes in the olive oil.
Thinly slice the shallots and separate the rings. Toss them into the bowl with the potatoes and toss again to coat. Add the rosemary and mix. Season with salt and pepper.
Spread the potatoes evenly, preferably in a single layer, on the baking sheet.
Bake the potatoes for 40 - 50 minutes, turning the potatoes every 10 minutes, until they are browned & mostly crispy.