Melt the butter in a large pot or Dutch oven over medium heat.

Add the sliced leek and fennel to the pot. Sauté for about 5-6 minutes until softened but not browned.

Sprinkle the flour over the vegetables and stir well to coat. Cook for 1 minute to remove the raw flour taste.

Slowly pour in the fish stock while stirring constantly to prevent lumps from forming.

Add the julienned carrots and the pinch of saffron threads to the broth.

Bring the mixture to a gentle simmer and cook for 10-12 minutes, or until the carrots are tender.

Stir in the heavy cream and bring the soup back to a simmer.

Gently add the fish chunks to the pot. Lower the heat and poach the fish for 5-7 minutes until opaque and flaky. Do not boil vigorously to keep the fish intact.

Remove the pot from the heat. Stir in the fresh lemon juice and chopped dill.

Season generously with salt and black pepper before serving hot.