For the shell stock: In a large saucepan over low heat, add the oil and sweat the prawn shells with the onion, thyme, bay leaves, peppercorns, lemon, and tomato for 2 to 3 minutes. Add the white wine and water and simmer for 45 minutes. Strain and reserve.
For the chowder: In a large saucepan over low heat, add the oil and sweat the onions with the bacon and celery for 5 to 6 minutes. Add the potatoes and sweat for another 5 minutes. Add the thyme, shell stock, and cream and bring to a simmer for 15 to 20 minutes. Add the salmon and season with salt, pepper, and lemon juice. For service, garnish with tarragon and chives.
Recipe courtesy of Dan Bugge and Chet Gerl