To a large skillet, add the oil, onion, and sauté over medium-high heat until the onion begins to soften about 5 minutes; stir intermittently.
Add the chicken and cook to sear for about 2 minutes; flip often to ensure even searing.
Add the garlic, ginger, coriander, and cook for about 1 minute, or until fragrant; stir frequently.
Add the sweet potatoes, coconut milk, Thai curry paste, salt, pepper, and stir to combine. Reduce the heat to medium-low, cover, and allow mixture to gently boil for about 5 minutes. Remove the lid and allow mixture to boil, uncovered, for about 5 minutes or until sweet potatoes are done.
Add the lime zest, lime juice, cilantro, stir to combine, and taste.
Optionally or as desired, add brown sugar. I find the brown sugar balances the lime zest and juice and I enjoy some light sweetness but if you do not, omit it. Also, if desired, add additional curry paste, salt, pepper, etc. to taste.
Serve immediately and optionally with rice.
