Grilled Herrings with Braised Lentils and Mustard Seed Sauce

Grilled herrings whole on the bone with a separate hot English mustard sauce was one of the very first dishes I was taught as a young chef. They were very nice to eat, but hard work. So, to simplify everything for the diner, I decided to take them off the bone and try them just with the sauce. I then needed something to eat with them, and mashed potatoes worked very well, but I find lentils even tastier.