Wash the chicken fillets, dab dry and cut into thin slices. Peel and chop the onion. Heat oil in a pot and fry the chicken slices in portions. Remove, season with salt and pepper and put aside.
Sauté the onion in the frying fat. Add tomato paste, sweat briefly and deglaze with stock. Add lentils, chilli pepper and bay leaf and simmer for about 30 minutes. In the meantime wash and clean the peppers and cut them into medium sized pieces.
Add the peppers about 15 minutes before the end of the cooking time. Cut pineapple into bite-sized pieces. Add the chicken slices and pineapple pieces approx. 5 minutes before the end of the cooking time and warm them up. Season with salt, pepper, chilli powder and vinegar to taste.
Serve lentil chili with crème fraîche and taco chips as desired.