Melt in a soup pot over medium heat:
Add and cook, stirring, until the leeks are tender but not browned, 6 to 8 minutes:
Stir in:
Bring to a boil, then reduce the heat and simmer until the potatoes are tender, about 15 minutes. Reduce the heat to low. Add:
Simmer just until the salmon is cooked, 8 to 10 minutes. Break apart the fillet with a spoon. Serve garnished with: