Preheat your oven to 350°F (180°C). Prepare the whole head of garlic by peeling away the outer layers and slicing off the top. Drizzle it with olive oil, season with a pinch of salt, and wrap it tightly in foil. Roast in the oven for about 30 minutes, until it feels soft and fragrant.

While the garlic is roasting, wash and thinly slice the leeks, discarding the dark green tops. Then, chop the sweet potatoes into 1/2-inch cubes.

In a large pot, heat a splash of olive oil over medium heat. Add the sliced leeks and sauté gently for approximately 5 minutes until they become tender.

Once the leeks are softened, add the curry powder, chili powder, turmeric, ground cardamom, and a pinch of sea salt. Sauté for 2-3 minutes.

Stir in the diced sweet potatoes, vegetable broth, crushed tomatoes, and tomato paste. Bring to a boil, then reduce heat and simmer uncovered for about 30 minutes.

With just 5 minutes left, unwrap the roasted garlic and squeeze the softened cloves into the pot. Stir to incorporate.

Blend the soup until smooth and creamy using a stick blender, tasting and adjusting seasoning as needed.

Ladle the soup into bowls and swirl in coconut milk. Top with fresh watercress and serve.