Add onion and cook over medium heat for 2-3 minutes or until soft.
Add garlic and cook for 1 minute more.
Add pumpkin, potato, lentils and stock.
Bring to the boil, reduce heat to low, and cook, covered, for 15 minutes, stirring occasionally.
Add the silverbeet and cook another 5 minutes.
Meanwhile, spray a nonstick frying pan with oil, and cook the lamb for 5 minutes on each side.
Transfer to a plate, cover loosely with foil and stand for 5 minutes.
Finely slice the meat across the grain; add to soup and heat through.
Season with freshly ground black pepper, and serve with crusty bread.
Note: The pumpkin weight is for the whole piece, including skin and seeds.
HINT: For a vegetarian soup, omit the lamb and use vegetable stock; served with bread, it provides complete protein. This soup will keep for up to 2 days in the fridge, or freeze for up to 2 months. Place individual portions in airtight containers. Thaw frozen portions in the fridge for about 10 hours (transfer from freezer to fridge in the morning to eat that night).