With a color combination as stunning as this, no one is looking for the fried potato chips. Kale is like popcorn—salty and crunchy and disappears in your mouth. The sweet potatoes are mellow and crunchy.
Position an oven rack in the center of the oven and preheat the oven to 350ºF.
Using a mandoline slicer or a sharp knife, slice the potato into ⅛-inch-thick slices. Put in a bowl and drizzle with 1 tablespoon of the olive oil. Toss well. Arrange in a single layer (without overlapping) on parchment-lined baking sheets.
Bake for 12 minutes. Turn the slices over and continue to bake, checking every 2 minutes, until brown and crisp, 6 to 8 minutes longer. Season the chips with ½ teaspoon of the salt and ⅛ teaspoon of the pepper.
Remove the thick stem from the kale leaves and discard. Cut the leaves into 2- to 3-inch pieces. Put in a bowl and drizzle with the remaining 1 tablespoon olive oil. Toss well. Arrange the kale in a single layer on parchment-lined baking sheets.
Bake the kale until crisp and slightly dark on the edges, 10 to 12 minutes. Season with the remaining ¼ teaspoon salt and ⅛ teaspoon pepper.
Let the chips cool before serving.