1 pound cod, (see Tip) or haddock, cut into 4 portions
2 large egg whites, beaten
¼ tsp. salt
¼ cup all-purpose flour
2 cups cornflakes
1½ tsp. Cajun or Creole seasoning, divided
4 tsp. canola oil
1½ pounds russet potatoes, scrubbed and cut into ¼-inch-thick wedges
Canola or olive oil cooking spray