Purists buffet will inform you this just receives higher with time, so put together it earlier of your celebration.
- 4 pickled herring fillets, sliced into 1/4″ pieces
- 1/4 medium onion, finely chopped
- 1/4 small fennel bulb, finely chopped
- 1 cup sour cream
- 2 tablespoons whole-grain Dijon mustard
- 2 tablespoons finely chopped fresh chives
- 1 tablespoon finely grated peeled horseradish or 2 teaspoons prepared horseradish
- 1 tablespoon fresh lemon juice
- Kosher salt, freshly ground pepper
- 8 slices dark seeded bread or rye bread, cut into squares or triangles
- Fresh parsley leaves (for serving)
- Mix pickled herring, onion, fennel, sour cream, mustard, chives, horseradish, and lemon juice in a small bowl; season with salt, pepper, and more lemon if desired. Transfer to a large jar; cover and chill at least 12 hours and up to 2 weeks. Serve herring mixture on bread topped with parsley.