Soak the lentils overnight in two changes of water. Boil in fresh salted water for about 15 minutes, or until tender, drain and keep hot.
Shallow-fry the onion, bacon and carrot in a little butter. Add the lentils, half the stock and a little red wine. Stir in the rest of the butter, in small pieces, to thicken.
In two hot pans shallow-fry the kidney and sweetbreads separately.