Adapted from Vietnamese Home Cooking by Charles Phan. You can roast the veggies instead of grilling them. See notes.
Variation: if you don’t have a grill, you can roast the veggies in the oven. Omit the scallions. Cut the eggplant into 1-inch pieces. Toss with 2 tablespoons olive oil and turn out onto a parchment-lined baking sheet. Roast in a 425 degree oven for 30 to 40 minutes, until soft and deeply caramelized. Thinly slice the leeks and toss with another tablespoon of olive oil. During the last 15 minutes of cooking, add leeks to the pan with the eggplant.