How to Make It
Place garlic and chiles in a mini food processor; pulse until finely chopped. Scrape into a small bowl, and whisk in lime juice, fish sauce, and sugar.
Heat 1/4 cup olive oil in a small skillet. Add scallions, season with salt, and cook, stirring occasionally, until softened, about 5 minutes. Scrape into a medium bowl. Stir in remaining 1/4 cup olive oil.
Preheat a grill to medium-high (about 450°F) or heat a grill pan over medium-high, and brush grate with oil. Brush fish with oil; season with salt and pepper. Grill, basting with scallion mixture, until just opaque, about 15 minutes per side. Transfer to a platter and top with remaining scallion mixture. Serve with garlic dipping sauce, cucumber, herbs, and rice.