Place the porcinis in a small saucepan, cover with the chicken stock and bring to a simmer over medium heat. Let simmer and reconstitute for 10 to 15 minutes. Using a slotted spoon, transfer the porcinis to a cutting board and chop them. Reserve the cooking liquid.
Heat the olive oil in a large Dutch oven over medium-high heat. Add the pancetta and cook until crisp. Using a slotted spoon, transfer the pancetta to a paper-towel-lined plate. Add the carrots, onions and garlic to the pan and cook for a few minutes. Add the chicken livers and hearts, sprinkle with salt and pepper and cook for 5 to 7 minutes. Add the sage, juniper, rosemary, bay leaf and tomato paste and cook, stirring, for 1 to 2 minutes. Add the red wine and vermouth and let simmer for 1 minute. Add the tomatoes, breaking them up with a wooden spoon. Add the porcini liquid, making sure the grit in the bottom of the pot does not get added. Stir and then let the ragu simmer for 30 to 45 minutes.