Cut sweet potatoes into 1/16-inch-thick slices, using a mandoline. Pour peanut oil to depth of 3 inches into a Dutch oven; heat over medium-high heat to 300°. Fry potato slices, in small batches, stirring often, 4 to 4 1/2 minutes or until crisp. Drain on a wire rack over paper towels. Immediately sprinkle with desired amount of kosher salt. Cool completely, and store in an airtight container at room temperature up to 2 days.