Place the lentils, sage, and one garlic clove into a pan and cover with water.
Boil the mixture, then simmer for 30 minutes until lentils are tender.
Drain the lentils and season with salt, pepper, lemon juice, and olive oil.
Boil the chard in salted water for 2 minutes until tender, then drain.
Stir-fry the chard with olive oil, garlic, and chilli for one minute in a hot pan.
Fry the butter, pancetta, and sage in a large pan for two minutes until crispy.
Add the liver slices and cook for one minute on each side before plating.
Wipe excess fat from the pan, then whisk in balsamic vinegar and crème fraîche for one minute.
Arrange the chard and lentils on the plates with the liver.
Pour the balsamic sauce over the dish to serve.