If your salmon has skin, use a thin sharp knife to remove it.
Spread 2 teaspoon Dijon mustard on each salmon fillet. In a medium bowl, combine frozen shredded hash browns (not thawed), flour, and ¼ teaspoon each salt and pepper.
Sprinkle the hash brown mixture on top of the mustard, pressing gently to help it adhere. You can also spray a little cooking spray on top of the hash browns and pat a few more on top to get them to stick.
Heat olive oil in a nonstick skillet and quickly flip the fish into the pan, potato-side down. If desired, sprinkle a little additional salt & pepper, to taste, on the non-potato side of the fish. Cook on the potato side for about 5-7 minutes, then turn carefully to keep potato crust in place. Cover pan and cook about 3 minutes more, until golden brown and opaque throughout (I used fillets about 1 ¼ " thick and they took 7 minutes on the potato side to brown nicely and then 3 minutes on the other side.)
I served this with a pea salad which consisted of thawed frozen peas, slices radishes, lemon zest, sliced green onion, chopped parsley, olive oil, lemon juice, salt & pepper. This salad can be served chilled or at room temperature. Other great side options would be cooked peas with chopped fresh mint or snipped dill, or roasted asparagus.
