In a large skillet that can handle some serious heat, melt a generous amount of healthy cooking fat over high heat.
While the pan is heating, pat the roast real dry and sprinkle it generously with salt and pepper, then place the roast in the hot pan and sear it on both sides without moving it until a beautiful golden crust forms, about 3 minutes per side.
Meanwhile, mix the carrot juice, tomato paste, Dijon mustard, salt and pepper together in a large glass measuring cup. Whisk vigorously until well combined and set aside.
Remove the seared meat to a 7 quart Dutch oven and place the skillet back over the heat source. Lower the heat to medium and add the onions and garlic; cook for about 4-5 minutes or until the onions start to turn soften and color slightly, then pour in the carrot juice concoction. Whisk well do deglaze the pan, simmer for about 1 minute then transfer to the Dutch oven. Throw in a few sprigs of fresh sage and time, put the lid on and bake in the preheated oven for 2½ hours.
After that time, take out the herbs and remove the bones from the roast, if present. Add carrots and garlic and return to the oven; continue cooking for a further 45 to 60 minutes, until carrots are fully cooked and the meat is tender enough to be pulled apart with a fork. Tear the meat into smaller pieces using two forks, then garnish with fresh chopped parsley if desired and serve.