Showstopping Swedish savoury celebration cake: a dark buttered kavring bread crust layered with a chilled mousse of matjes herring, sour cream, cream cheese, red onion, chives, and dill.
Mix crushed kavring crumbs with melted butter. Press firmly into the base of a 22cm springform cake tin lined with parchment paper. Chill 15 minutes.
Soak gelatin leaves in cold water for 5 minutes. Warm 50ml gräddfil in a small pan, dissolve squeezed gelatin into it, then whisk into remaining gräddfil and cream cheese.
Fold diced matjes herring, minced red onion, chives, dill, and white pepper into the cream mixture. Pour over the crust and smooth the top.
Refrigerate for at least 4 hours (or overnight) until set. Release springform ring and garnish with chopped hard-boiled eggs, lumpfish roe, and dill sprigs.