For the bollito misto:
1) Heat a large braising pot over medium-high heat. Season the beef with salt and pepper. Sear the beef, browning it on both sides, about five minutes a side.
2) Carefully add the stock and enough water to just cover the meat. Add the onion, celery, and bay leaf. Bring the liquid to a boil. Lower the heat to a simmer, cover, and cook for one hour.
3) Add the carrots and potatoes and cook until the meat is tender, about another hour.
4) Carefully lift out the meat, place on a cutting board, and cover with foil. Strain the vegetables from the stock. Discard the celery, onion, and bay leaf. Arrange the carrots and potatoes on a platter and cover with foil to keep warm.
5) Continue cooking the stock uncovered over medium heat until reduced by half, about 20 minutes. Meanwhile, slice the meat against the grain, on an angle. Arrange the meat alongside the carrots and potatoes on the platter.
6) When the stock has reduced, season with salt and pepper, to taste, and transfer to a gravy dish.
7) Serve the bollito misto with the gravy and bowls of the gorgonzola sauce and the salsa verde.
For the gorgonzola sauce:
1) Put all the ingredients in a food processor and combine until smooth. Serve in a side dish.
For the salsa verde:
1) In a bowl, stir all the ingredients together until combined. Serve in a side dish.