Brown chicken breast in 1 Tbsp oil in a large, heavy saucepan over medium heat. Remove chicken and set aside.
Add remaining 1 Tbsp oil to pan; stir in onions. Cook, string frequently, until onions are golden brown, about 15 minutes.
Stir in the remaining ingredients, except parsley and chicken breasts. Bring to a boil; cover and simmer for 15 minutes.
Arrange chicken breasts on top of lentil mixture; cover and simmer another 8-10 minutes, until chicken breasts are cooked thoroughly and lentils are tender. Sprinkle with parsley and serve.