Melt butter in a 1 qt skillet over medium-high heat.
Add onion & cook until translucent - about 2 mins.
Add flour & cook for 30 more seconds.
Stir in broth or stock.
(If desired) stir in 1 cup water. This will result in a thinner soup.
Add potatoes.
Bring to a boil then reduce to a simmer & cover for 10-15 mins. Potatoes should be fork-tender.
While waiting, cut salmon into 2-inch pieces.
Add salmon and corn to skillet simultaneously, then cover for 3 more minutes.
Stir in cream, mustard, and seasoning. Warm & Serve.
