Boil the cannellini in plenty of cold water with a sprig of rosemary for about an hour and a half; salt only towards the end of cooking and then drain. Cut the onion and brown it in a large pan with a little olive oil and half a glass of water. After a few minutes add the pumpkin and the potato cut into cubes and the black cabbage cut into strips (remove the central grain). Cover with about 2,5 liters of water and let cook for 30 minutes. Towards the end of cooking, salt, pepper and add half a portion of boiled cannellini whole and half a portion smoothed with a drizzle of oil. Let the soup goes for another 5-10 minutes.
Clean the shrimp tails by removing the carapace and intestine, salt and pepper them slightly, wrap each tail with a slice of bacon and bake at 180ºC for about 10 minutes (until the bacon becomes crisp). Serve the soup with the bacon shrimp tails.