Heat vegetable oil in a large pan or wok over medium-high heat.

Add the sliced onions and cook until they start to soften, about 2 minutes.

Stir in the minced garlic, grated ginger, and optional sliced red chili. Cook for another minute until fragrant.

Add the thinly sliced carrots to the pan. Stir-fry for about 5-7 minutes until the carrots are tender but still have a slight crunch.

In a small bowl, mix together the soy sauce, rice vinegar, sesame oil, and brown sugar until the sugar dissolves.

Pour the sauce over the stir-fried carrots and toss to coat evenly. Cook for another minute to heat through.

Taste and adjust seasoning with salt if needed.

Garnish with fresh coriander if desired.

Serve hot as a side dish or over cooked rice as a main meal.