What could be better than homemade potato chips? If you’re used to snacking from a bag, eating these crunchy, kettle-style treats will be like tasting potato chips for the first time. They're great with Michael Ruhlman's creamy French onion dip. (His secret for perfectly caramelized onions? A little butter and a lot of patience!)
French Onion Dip: To dice onions, trim the top and bottom, slice in half lengthwise, and discard skin. Lay the flat sides down and make vertical cuts, just short of the root to keep the onion intact. Stand the onion up and make several slices perpendicular to your first cuts, creating a grid that will result in an even dice. Place the onion flat side down again and slice across into a uniform dice. Place diced onions into a bowl and set aside.
In a medium skillet over high heat, melt the butter. Then add diced onions and a generous pinch of salt. Stir and sauté until onions begin to sweat, about 3-5 minutes. Reduce heat to medium-low and continue cooking, stirring occasionally, until onions are golden brown and caramelized, 20–30 minutes. Set aside to cool, 10–15 minutes. (Makes ½-⅔ cup caramelized onions.)Meanwhile, start the potato chips.
In a large, heavy pot or Dutch oven over medium-high heat, add enough oil to fill halfway. (You may not need all of the oil.) Clip a deep fry thermometer onto the side of the pot and heat oil to 350 F. Assemble the dip: Stir lemon juice into the cooled caramelized onions. Add ½ cup of the onions and a pinch of cayenne to the crème fraîche, then stir to combine; add a pinch of salt. Stir, taste, and adjust seasoning; finish with chives and set aside.
Potato chips: Line a large bowl with two layers of paper towel to drain the chips. Trim and discard the ends of each potato. Adjust mandoline setting to 1/16-inch thick (about the thickness of a dime), then carefully slice the potatoes. Quickly but gently place ⅓ of the potato slices into the oil, one by one; spreading them out will help them fry flat and prevent sticking. (Since the chips fry so quickly, it’s useful to have a second person add slices at the same time, to encourage even cooking in larger batches.) Stir and flip the potatoes with the spider strainer to separate. Then let the potatoes fry, stirring, separating, and flipping the chips as needed, and adjusting the heat to keep the temperature at 350 degrees F. Chips are done when they're a deep golden color, 4–6 minutes.
Transfer the chips to the paper towel-lined bowl. While the chips are still hot, sprinkle with salt while shaking to bowl to season evenly. (Seasoning and tossing immediately after frying will help chips dry while absorbing salt.) Repeat in two batches with remaining potatoes. Serve with dip.