In a large soup pot or Dutch oven, melt 3 tablespoons of unsalted butter over medium-high heat. Add the sliced carrots and leeks, seasoning with ½ teaspoon of kosher salt. Cook for 8-10 minutes, stirring occasionally, until the vegetables are softened and fragrant.

Once the vegetables are tender, stir in the cubed Yukon Gold potatoes and pour in 4 cups of seafood stock. Bring the mixture to a gentle boil over medium heat, then reduce the heat and let it simmer for 10-15 minutes until the potatoes are fork-tender.

Gently add the 1-inch cubes of fresh salmon to the pot, along with ¾ cup of crème fraîche. Stir well to combine and cover the pot. Allow the soup to simmer for 3-5 minutes, just until the salmon is cooked through.

Remove the pot from the heat and stir in the chopped fresh dill, adjusting the seasoning with additional salt and freshly ground black pepper if needed. Ladle the soup into bowls and garnish each serving with extra dill and a sprinkle of pepper.