Peel the onion and finely dice. Cut the carrot and the leek in to thin slices. Rinse the lentils.
Sweat the leeks, onion and carrots in a saucepan with 2/3 of the butter. Add the garlic, thyme, bay leaf and the lentils and then pour in water to 2cm above the height of the vegetables. To prevent the lentils from hardening, do not season at this point. Cook over a medium heat for 30 minutes. Add the cream, bring to the boil then blend. Strain through a fine sieve if necessary then season with salt and freshly ground pepper.
Heat a frying pan and sauté the pine nuts with the rest of the butter. Once golden, remove from the pan and place on some kitchen towel to absorb any grease.
Heat the same frying pan to hot and then cook the foie gras slices for 2 minutes on each side.
Serve the foie gras in deep plates or soup bowls. Sprinkle over the pine nuts then top with the hot lentil puree.
«To prevent the foie gras slices from 'melting' when cooked, feel free to freeze them and cook directly after removing from the freezer.»