In large, wide saucepan on medium-low heat, add olive oil and sweat onions, leek, and celery for about 2 minutes, or until just wilted. Add garlic and sauté over medium heat for a further 2 to 3 minutes. Add potatoes, pepper, thyme, fennel, bay leaves, tomatoes, and mustard and stir well to combine. Add in stock and simmer gently for approximately 15 minutes, or until potatoes can be pierced easily with fork. Add smoked salmon and asparagus and cook for a further 5 minutes. Finally, add in peas.