Heat oil in a large soup pan over a medium-high heat.
Gently saute the onion until it begins to soften, about five minutes.
Stir in the black mustard seeds, coriander seeds and curry powder. Cook for one minute and add the ginger, smoked sea salt and cubed vegetables. Stir well to coat.
Pour over the vegetable stock, pop the lid half on and leave to simmer for 20 minutes or so, until the vegetables are tender.
Squeeze in the lemon juice, remove from heat and blend the soup with a hand blender until smooth. Season well with freshly ground black pepper.
Serve warm with plenty of crispy onions.
Notes
Tip: keep ginger root in your freezer. Grate the desired quantity, no need to peel, and return to freezer to keep fresh.