Add the olive oil to a pressure cooker and, once hot, add the crumbled sausage. Saute the sausage until the meat is caramelized and most of the fat has rendered from it, about 4 to 5 minutes. Using a slotted spoon, remove the sausage from the pan and transfer to a plate. Set aside. Add the lamb meat to the pan and sear until caramelized, about 4 to 5 minutes. Remove the lamb from the pan and transfer to the plate with the sausage. Add the onions, carrots and celery to the pan and cook, stirring occasionally, until tender, 3 to 4 minutes. Add the garlic and beans and cook, stirring, for 1 minute. Add the rosemary, chicken stock, reserved sausage and lamb meat to the pan and stir to combine. Place the lid on the pan and, when a steady stream of steam is emitted from the lid, reduce the heat to low and cook for 1 1/2 hours, or until the beans and lamb meat are tender. Remove the lid, season with salt and pepper, to taste, and garnish with the parsley. Serve with garlic bread.