Heat coconut oil in a large skillet over medium heat. Add diced onion and cook for 4 to 5 minutes until softened and translucent.
Stir in the minced ginger, red chili, and garlic. Sauté for an additional 2 minutes until fragrant.
Pour in the coconut milk and stir in soy sauce, red curry paste, brown sugar, salt, and pepper. Mix well until the sauce is smooth and flavorful.
Carefully add the thinly sliced chicken to the skillet. Reduce heat to medium-low and let the chicken gently poach in the sauce for 15 to 20 minutes, or until fully cooked and tender. Avoid boiling the sauce to preserve the chicken’s texture.
Once done, remove from heat. Stir in a splash of fresh lime juice and chopped cilantro if desired.
Serve the coconut milk chicken over your choice of rice or noodles. Top with chili oil, scallions, or additional cilantro for extra flavor.