Combine lentils and boiling water in a large jug. Set aside.
Heat oil in a large saucepan on medium. Cook onion for 2 minutes, until soft. Add lentils and soaking water, carrot, kumara, broccoli and 6 cups water. Bring to boil. Reduce heat to low and simmer for 30 minutes, until vegetables are tender. Cool slightly.
Using a hand blender, blend until smooth. Season to taste. Serve topped with green onion and a dollop of natural yogurt.