¼ cup citrus juice (any combination of lemon, lime, grapefruit and orange juice; preferably at least half lemon juice)
¼ cup rice vinegar
¼ cup water
One 6-inch piece kombu
¼ cup tightly packed dried bonito flakes
2 Japanese eggplants (each 8 to 10 inches long), ends removed and halved lengthwise
Eight 6-inch wood skewers
2 bricks wrapped in aluminum foil
1 tablespoon fine sea salt
⅛ teaspoon sansho pepper
Sake in a spray bottle (preferably Junmai sake)
Directions
To a small saucepan add the sake and mirin and bring to a boil over high heat. Boil for 1 minute, remove from the heat and cool the liquid to room temperature.
In a medium bowl, add the soy sauce, citrus juice, vinegar, water, the sake mixture, kombu and bonito flakes. Stir to combine, then cover the bowl with plastic wrap and refrigerate for at least 12 hours or overnight.
Strain the ponzu through a cheesecloth-lined sieve, gently pressing on the solids to extract the liquid. Transfer the ponzu to an airtight container and refrigerate until using (the ponzu will keep refrigerated for up to 2 weeks).
Turn each eggplant sliced-side down. Use a sharp knife to make a shallow crosshatch pattern into the skin and over the entirety of each eggplant, then slice the eggplant crosswise into 1½ to 2-inch pieces. Double skewer the eggplant pieces, threading about 3 pieces onto each set of skewers.
Heat a charcoal or gas grill over medium-high heat and set the bricks on the grill about 4 inches apart. In a small bowl mix the salt with the sansho pepper. Spritz the cut-side of the eggplant with sake, then season with the sansho-salt. Set the eggplant on the bricks cut-side facing down so the ends of the skewers rest on the bricks and the eggplant is elevated off of the grill grate. Cook until browned, 2½ to 3 minutes. Turn the skewers over, spritz the eggplant with sake, season with sansho-salt and cook until the skin is browned, 1½ to 2 minutes longer. Remove from the grill and serve warm with the ponzu sauce on the side.