In Iceland, dried catfish is often eaten as a snack, similar to potato chips or popcorn in the U.S. Try it as a shredded topping with this buttery appetizer from Gunnar Gialason, chef and owner of Dill Restaurant.
Make the hazelnuts: Preheat oven to 350 degrees. Fill a medium saucepan with 2 cups plus 2 tablespoons water; add salt and bring to a boil. Let boil until water is reduced by half. Add hazelnuts and cook, stirring, 2 minutes. Drain using a fine-mesh sieve and let stand 5 minutes. Place hazelnuts in an even layer on baking sheet and transfer to oven; bake until dried, about 15 minutes.
Make the dill oil: Meanwhile, place sugar and vinegar in a small saucepan and bring to a boil over medium heat; cook until thick and syrupy, about 8 minutes. Remove from heat and set aside to cool.
Place dill and grapeseed oil in the jar of a blender; blend until well combined. Strain and return liquid to blender; discard any solids. Add sugar syrup and blend to combine.
Make the creamy butter: Melt butter in a medium skillet over medium-high heat. Continue cooking until butter goes from golden and fragrant to just burned; immediately remove from heat and let cool.
Bring a large pot of water to a boil. Prepare an ice-water bath. Place eggs in boiling water and cook for 4 minutes; drain and immediately transfer to ice-water bath to cool. Crack cooled eggs into the clean jar of a blender. Add cooled burned butter, vinegar, and salt; blend until emulsified.
Make the hardfiskur: Place dried catfish in the clean jar of a blender; blend until shredded.
To serve, place a small dollop of creamy butter on each of 12 small plates or soup spoons. Drizzle dill oil over each dollop and top with shaved dried catfish. Grate salted hazelnuts over fish and serve.