Cut the chicken breasts into 3/4-inch pieces and season with salt and pepper.
Heat the extra-virgin olive oil in a large skillet over medium heat. Add the chopped onion and cook for 5–7 minutes, until translucent.
Add the minced garlic and cook for another minute.
Add the chicken to the skillet, increase the heat to medium-high, and cook until browned on all sides but not cooked through, about 4 minutes.
Sprinkle the curry powder over the chicken and onions, stir to coat, and cook for 1 minute.
Pour in the coconut milk, chicken broth (or water), and tomato paste. Stir well and bring to a boil.
Reduce heat to low, cover, and simmer for 15–20 minutes. Uncover for the last 5 minutes if the sauce seems too thin.
Meanwhile, cook the basmati rice according to package instructions.
Serve the chicken curry hot, garnished with chopped fresh cilantro if desired.