Try to cut the fingerlings no larger than 1/8 inch thick, so that the potatoes will crisp in the oven. (Using a mandolin will allow you to cut them even thinner.) These crisps make a great accompaniment to grilled steak or roasted fish.
Position a rack in the center of the oven and heat the oven to 425°F. Line a large, rimmed baking sheet with parchment paper or aluminum foil. In a large bowl, toss the potato slices with the oil, shallots, rosemary, 1-1/4 tsp. salt, and 1/2 tsp. pepper, and then spread the chips flat on the baking sheet. Bake the potatoes, turning after 10 minutes, until they brown and start to crisp, 25 to 30 minutes; the shallots should be tender and browned. Serve immediately.
Photo: Maren Caruso