Cook the onion with the fat on a low heat with some sea salt until soft and golden, about 30 minutes.
2 tablespoon cooking fat, 1 large onion
In the mean time, in a stockpot, place the diced sweet potato, leek, spinach, chard and ginger with 4 cups of water and 1 teaspoon sea salt.
1 ½ teaspoon sea salt, 1 large leek, 1 big bunch spinach, 1 big bunch green Swiss chard, 1 large sweet potato, 3 tablespoon chopped fresh ginger
Bring to a boil and reduce to a simmer and let simmer until the vegetables are soft, about 30 minutes. Add the onions during the simmering process when they are ready.
Add the chicken stock and bring back to a boil.
2 cups chicken stock
Remove the pot from the heat, add the lemon juice and some black pepper to taste.
3 teaspoon lemon juice, Freshly ground black pepper to taste
Puree in a blender or food processor, making sure not to burn yourself with the hot liquid.
Serve in bowls with a wedge of lemon on the side and some extra grated ginger as a garnish if desired.