Heat the oil in a large frying pan or wok over medium-high heat.
Add the chicken and cook until browned on all sides, about 5-7 minutes. Remove the chicken from the pan and set aside.
In the same pan, add the onion and garlic and cook until softened, about 2-3 minutes.
Add the coconut milk, peanut butter, ground coriander, ground cumin, salt, and black pepper to the pan. Stir well to combine and bring the mixture to a simmer.
Add the cooked chicken back into the pan and stir to coat with the peanut sauce.
Reduce the heat to low and let the mixture simmer for 10-15 minutes, or until the chicken is cooked through and the sauce has thickened.
Serve the peanut butter chicken over steamed rice and garnish with fresh chopped coriander.