Heat a large pot over high heat, then sear flanken for two minutes per side. Set aside.

Add oil to the pot, then sauté onion and mushrooms until soft. Add peas, lentils, soup mix, salt, pepper, and eight cups of water. Bring to a boil.

Reduce heat to medium, return meat to pot, and simmer for one hour.

Then reduce heat to low and simmer for another two hours, until meat is very soft.

Serve hot with baguettes, if desired.