(Recipe #66, page 66)
After carefully picking over the lentils and washing them, boil them until completely soft. Then pour off all the water and add meat stock along with sliced leeks and celery; cook for a good while longer and thicken the stock with a roux of flour and plenty of fat.
Or drain the lentils after they have boiled for an hour and then boil them with fresh water until quite soft. Cut a piece of bacon and a lot of onions into slices, fry in butter until the butter begins to foam, add from 1 to 3 tablespoons of flour (depending on the quantity of lentils) and brown lightly, stir in meat stock to make a thick sauce, add vinegar, salt, and pepper, pour over the lentils, cook them until done in the sauce.
Translated by David Green.