Heat 2 tablespoons of oil in a large pot. Add leeks and sauté until tender, about 5 minutes. Then add garlic and carrots (optional) and cook another 3 minutes.
Pour in chicken stock, coconut milk, and season with turmeric, coriander, salt, pepper and bay leaf, stir and bring to a boil.
Reduce heat to moderately low. Add the cod. Cook until cod is cooked through, about 8 minutes
Discard bay leaf.
Ladle into individual bowls and garnish with scallions, cooked bacon and just a pinch of cayenne pepper.
If you're following a low-carb way of eating, you may want to eliminate the carrots.
To clean the leeks, cut off the dark green tough leaves. Next, cut a thin slice from the root and run the leeks under water to wash away all the soil from the inner layers. Finally, slice crossways up to the root end and discard the end.
If you're not low-carb and you're in the mood for a heartier soup, you could also add some diced up Yukon Gold potatoes at the beginning of your cooking right along with the leeks. The starch will add more body to your soup. However, you would have to cook the potatoes in your stock mixture until tender for about fifteen minutes before adding the cod.