In skillet, heat oil over medium-high heat. Add the ginger, chopped onions and garlic, cooking for about 5 minutes, or until onions are softened and translucent.
Sprinkle in flour, turmeric and curry powder. Stir, so the ginger, onions and garlic are coated in the flour and spice paste. Add chopped sweet potatoes, carrots, red pepper and celery.
Stir, incorporating all the crusty bits stuck to the bottom Pour in vegetable broth and spoon in tomato paste. Stir again and bring mixture to a boil.
Reduce heat to medium-low, and cover. Simmer, until sweet potato is tender and the sauce has reduced and deepened in color to a burnished pumpkin shade, about 30 minutes.
Season with sea salt and freshly ground pepper, then stir in the chopped greens. They’ll wilt right into the curry. Garnish with the optional chopped cilantro.