In a large, 12-inch nonstick skillet, heat the oil over medium heat until hot. Add the ginger and garlic and cook, stirring constantly, for about 30 seconds, until it starts to smell fragrant.
Sprinkle in the curry powder, coriander and cumin. Cook for another 30 seconds, stirring to prevent burning.
Add the chicken and cook until lightly browned, 2-3 minutes (it doesn't need to be cooked all the way through quite yet).
Stir in the coconut milk, brown sugar, fish sauce, salt and pepper. Bring the mixture to a simmer. Cook for 4-5 minutes until the chicken is cooked through.
If you would like the sauce a bit thicker, whisk together the cornstarch with 2 tablespoons cold water in a small bowl. Once combined, stir the mixture into the simmering curry. Simmer, stirring constantly, for a minute or so until the sauce thickens a bit.
Stir in the cilantro. Season with additional salt and pepper to taste, if needed. Serve the curry over hot, cooked rice, quinoa or whatever else you might like (or it can be served on its own).
