Step 1

Prepare an outdoor grill for medium, direct heat. Meanwhile, shuck 4 ears corn. Thinly slice 3 medium scallions. Heat 1/3 cup neutral oil in a small saucepan over medium-high heat until the oil is shimmering (test by dropping in a piece of scallion; it should barely sizzle). Add the scallions and cook, stirring constantly, until fragrant, 30 to 45 seconds. Remove the pan from the heat. Add 1 tablespoon granulated sugar and 1 teaspoon fish sauce and stir until the sugar is dissolved.

Step 2

When the grill is ready, scrape the grates clean if needed. Place the corn on the grill and grill uncovered until charred in spots, turning them every few minutes, 8 to 10 minutes total. Transfer to a plate. Brush the corn all over with the scallion oil. Serve with the remaining scallion oil.