Cut the pumpkin into 3cm / 2.25" slices. Cut the skin off and scrape seeds out (video is helpful). Cut into 4cm / 1.5" chunks.
Place the pumpkin, onion, garlic, broth and water in a pot - liquid won't quite cover all the pumpkin. Bring to a boil, uncovered, then reduce heat and let simmer rapidly until pumpkin is tender (check with butter knife) - about 10 minutes.
Remove from heat and use a stick blender to blend until smooth (Note 3 for blender).
Season to taste with salt and pepper, stir through cream (never boil soup after adding cream, cream will split).
Ladle soup into bowls, drizzle over a bit of cream, sprinkle with pepper and parsley if desired. Serve with crusty bread!