In a bowl whisk together the coconut milk and fish sauce. Set aside.
In a deep non-stick skillet or wok, stir fry the chicken until done. Transfer chicken to a plate.
In the same skillet/wok heat paste on medium until it becomes fragrant, about 3-4 minutes.
Next, add in the coconut milk mixture, and stir to combine.
Make a slurry to thicken the sauce: Mix 2 tsp of cornstarch with 2 Tbsp of the sauce. Whisk together in a small bowl.
Place the sauce and corn starch mixture (roux) back in the sauce and stir continuously until it has reached nappe consistency. Once the sauce has thickened add the chicken back in and simmer for 10 minutes.
Serve with jasmine rice and garnish chicken with lemon zest.