Step 1: Prepare the Aromatics

1. In a large pot or Dutch oven, melt the butter and olive oil over medium heat. The combination of butter and oil prevents the butter from burning and enhances the flavor.
2. Add the sliced leeks to the pot and sauté for 3-4 minutes until softened and fragrant. Stir occasionally to ensure even cooking.
3. If using garlic, add it to the pot and sauté for an additional 30 seconds until fragrant.

Step 2: Build the Soup Base

1. Add the diced potatoes and carrots (if using) to the pot. Stir them with the leeks to coat them in the butter and oil.
2. Pour in the fish stock (or chicken stock) and add the bay leaf. Season with salt and black pepper.
3. Bring the soup to a gentle boil, then reduce the heat to a simmer. Cover the pot and let the vegetables cook for 12-15 minutes, or until the potatoes are fork-tender.

Step 3: Add the Salmon

1. Gently stir in the salmon chunks, making sure they are submerged in the broth.
2. Cook the salmon for 5-7 minutes, or until it is opaque and flakes easily with a fork. Avoid overcooking, as the salmon will become dry.

Step 4: Create the Creamy Broth

1. Reduce the heat to low and stir in the heavy cream (or milk). If using smoked paprika, add it at this stage for a subtle smoky flavor.
2. Simmer the soup gently for 5 minutes to allow the flavors to meld. Avoid boiling the soup after adding the cream, as this may cause it to curdle.

Step 5: Finish with Dill and Lemon

1. Stir in the fresh dill and parsley (if using), along with the lemon juice. Taste the soup and adjust the seasoning with additional salt, pepper, or lemon juice, if needed.
2. Remove the bay leaf before serving.

Step 6: Serve and Garnish

1. Ladle the soup into bowls and garnish with additional dill, parsley, and freshly cracked black pepper.
2. Serve with lemon wedges on the side for extra brightness, along with crusty bread or rye bread for dipping.