1. Place potato in a small saucepan and add just enough water to cover. Bring to a boil over high heat, then simmer until tender and easily pierced with a fork, about 15 minutes. Drain.
2. While the potato cooks, in a medium bowl mix together mayo, mustard, and sriracha. Cover and refrigerate.
3. Trim the end off the leek and use the white and light green part only. Cut in half and rinse the layers to remove any grit. Finely mince. Heat 2 teaspoons of the oil in a large nonstick skillet over medium heat. Add leek and 1/8 teaspoon of the salt. Cook until the leek just begins to soften, about 2 minutes. Transfer to a large bowl.
4. Chop cod into large chunks and add to a food processor. Pulse for 30 seconds until cod is a coarse paste. When potato is cooked, add to cod and pulse until well combined. Add mixture to the bowl with the leeks. Add 1/4 cup of the bread crumbs, egg, pepper, and remaining 1/4 teaspoon salt, and mix well. Stir in corn, mushrooms, and chopped dill and mix until everything is well combined.
5. Form mixture into 12 patties about 1/2 inch thick and 3 to 4 inches across, using about 1/4 cup per patty.
6. Heat 1 Tbsp. oil in the skillet over medium-high heat. Dip each patty in the remaining 1/2 cup bread crumbs, then place in the skillet, being careful not to overcrowd. Fry each side until golden brown, about 3 to 4 minutes, then transfer to a paper-towel-lined plate and tent with foil. Heat remaining 1 Tbsp. oil in the skillet and cook remaining 6 patties.
7. To serve, transfer fish cakes to a serving platter. Put a small dollop of sauce on each cake, and garnish with dill sprigs if desired. Serve immediately, with additional sauce on the side.
Source: Hannaford Fresh Magazine - September - October 2012