In a large saucepan with a lid, steam sauté the onion in a small amount of water for 5 minutes on a medium heat. If it begins to stick, just add a bit more water and keep stirring.
Add the celery, potatoes, carrot, sage, rosemary, stock cube, lentils and water to the pan and bring to the boil.
Reduce the heat and cook, covered, for 10 minutes, stirring now and then. The potato should be just tender.
Add the broccoli and cook for a further 10 minutes (or until the lentils have become mush), stirring occasionally.
Add the Bragg's, salt and pepper to taste, and the leafy greens. Cook for 3 more minutes, or until the greens have wilted.
Serve immediately in bowls. (Also keeps well in the fridge for several days. Reheat when needed.)