Thai Chicken with Basil

Ingredients

• 1 1/2 cups lightly packed basil leaves
• 1 1/2 tablespoons soy sauce
• 1 1/2 teaspoons sugar
• 1 large onion, cut into thin slices
• 2 tablespoons Asian fish sauce (nam pla or nuoc mam); see Note
• 1 tablespoon water
• 1 1/3 pounds boneless, skinless chicken breasts (about 4), cut into 1-by-2-inch pieces
• 3 fresh red chiles, seeds and ribs removed, cut into thin slices, or 1/4 teaspoon dried red-pepper flakes
• 2 tablespoons cooking oil
• 3 cloves garlic, minced