1: Ember-roasting on a charcoal grill: Set up a charcoal grill for ember-roasting (caveman grilling). Rake out the coals in an even layer and lay the onions, eggplants, and peppers on the embers. Roast until charred black on all sides and tender in the center (a slender metal skewer will pierce the onions and eggplants easily). You’ll need 12 to 15 minutes for roasting the onions; 8 to 10 minutes for the eggplants and peppers. Turn with tongs so the veggies roast evenly. Ember-roast the celery, if using, for about 2 minutes per side; the scallions for 1 to 2 minutes.

Direct grill method: Heat your gas or wood-burning grill as hot as it will go. Direct grill the veggies until charred on the outside and cooked through (follow the cooking times above). Test for doneness with a metal skewer.

2: Transfer the charred vegetables to a large metal bowl to cool. Scrape off the burnt skins with a paring knife (don’t worry about removing every last bit—a few spots of black add color and flavor). Transfer the veggies to a cutting board and cut into 1-inch dice. Leave the vegetable juices in the bowl.

3: Make the dressing: Using a fork, remove any large pieces of skin from the vegetable juices in the bowl. Add the sherry vinegar and salt and pepper (about 1/2 teaspoon of each) and whisk until the salt crystals are dissolved. Whisk in the olive oil. Taste for seasoning, adding vinegar or salt to taste; the dressing should be highly seasoned.

4: Return the diced grilled vegetables to the dressing and toss to mix. To serve, mound the salad onto a platter or plates. Sprinkle each serving with hazelnuts (if using) and parsley.