Cut chicken into bite-sized pieces. Dice the onion.
Heat oil in a large skillet over medium-high heat. Add the chicken, salt, pepper, and half of the curry powder. Cook for about 5 minutes, or until chicken is browned. Remove cooked chicken to a plate.
Turn the heat to medium and add the diced onion. Saute for about 5 minutes, or until tender. Add the garlic and cook 30-60 seconds.
Add the coconut milk, the last tablespoon of curry, the cumin, coriander, and chicken base. Cook and stir over medium heat until slightly thickened, about 3-5 minutes.
Add the cooked chicken and any juices back to the pan. Simmer for 5-8 minutes, or until heated through.
Serve hot over rice. If desired, garnish with chopped cilantro.