Step 1

In a food processor or blender, combine the garlic, onion, fish sauce, sugar and 1 teaspoon each salt and pepper. Process until mostly smooth, about 1 minute. Transfer to a large bowl.

Step 2

Using a sharp knife, cut four parallel slashes on each chicken leg, 2 on the thigh and 2 on the drumstick, slicing through the skin all the way to the bone. Flip each leg and repeat on the underside. Transfer to the marinade and toss to coat, rubbing it into the slashes. Let stand at room temperature for 20 minutes or cover and refrigerate overnight.

Step 3

Heat the oven to 450°F with a rack in the middle position. Line a rimmed baking sheet with foil and spread 1 cup salt over it. Mist a wire rack with cooking spray, then set over the salt. Remove the chicken from the marinade, shaking off the excess, and arrange skin up on the prepared rack. Roast until well browned and the thickest part of the thigh reaches 175°F, 20 to 25 minutes.