Finely chop the scallions, garlic, and grate the ginger. Place them in a heat-proof bowl or glass jar.
Heat the neutral oil in a small saucepan over medium-high heat until shimmering (about 2–3 minutes).
Carefully pour the hot oil over the scallions, garlic, and ginger. You’ll hear a sizzle as the aromatics cook and infuse the oil.
Add soy sauce, sesame oil, salt, and rice vinegar (if using). Stir well to combine.
Taste and adjust seasoning if needed. Let the sauce cool to room temperature.
Transfer the sauce to a clean jar or bottle. Store in the refrigerator for up to 2 weeks.
