Heat oil in a large saucepan over a medium heat. Add the fennel and mustard seeds and cook for a minute or so or until they start to pop.
Add celery, garlic, ginger, turmeric and curry powder. Cook for a few minutes – or until the celery starts to soften.
Add the zucchini, carrot, sprouts and quinoa, and stir to coat in the spice mixture.
Stir in the tomatoes, capsicum, stock and 2 cups water. Bring to the boil, then reduce the heat and allow to simmer for 20 minutes. Stir through the coriander leaves and season to taste.
To serve – divide the soup among serving bowls and top with extra coriander and a spoonful of yoghurt.