Make a paste by smashing the garlic with a little salt and add to a small bowl. Whisk in the vinegar, soy, sesame oil, and red chili flakes.
Heat grill to high. Brush eggplant with oil and season with salt and pepper. Grill until slightly charred and just cooked through. Slice each half into 1/2-inch slices and place on a platter. Drizzle with the vinegar mixture and sprinkle with mint or cilantro.