Heat the oil in a frying pan over a medium heat, add the carrot, celery and onion and cook for 2–3 minutes, then stir in the sage, garlic and lentils. Pour in the wine, add the spinach and crème fraîche and cook for 8–10 minutes.
Meanwhile, cook the bacon under a preheated medium grill for 7 minutes or until crisp, then chop roughly.
Season the liver with salt and pepper. Place under a hot grill or on a hot griddle and cook for 1–2 minutes on each side.
Serve the liver on a bed of lentils, sprinkled with the chopped bacon.