Rinse the chickpeas and drain them very well. Line a baking sheet with a couple layers of paper towels and turn the chickpeas out on top in a single layer. Let the chickpeas dry thoroughly, at least 1 hour and up to 4 hours (the drier the better).
Fill a medium pot with vegetable oil to a depth of 2 inches. Bring the oil to 350 degrees F over medium-high heat. Add the sage leaves and fry until a shade darker and crisp, 30 seconds to 1 minute. Transfer to a paper-towel-lined baking sheet and sprinkle with a little salt.
Add half of the chickpeas to the oil and fry, stirring often, until golden brown and crisp, 2 to 3 minutes. Transfer to a paper-towel-lined baking sheet and sprinkle with salt and pepper. Return the oil to 350 degrees F and repeat with the remaining chickpeas. Cool completely.
Gently toss together the fried chickpeas and sage, the Parmesan, and salt and pepper to taste.