Bash the allspice berries once each with a rolling pin to slightly crush them. Add them and the potatoes to the broth, bring to the boil again and simmer for around 12 minutes or until the potatoes are just tender. Add the salmon and continue cooking for another 2 minutes or until the fish is cooked through. Season with salt and pepper, stir in the butter and cream, bring back to a simmer and then serve in two bowls. Divide and sprinkle half the dill on top of each portion.