Scrub and debeard the mussels, discarding any that are cracked. Tap any open mussels on a work surface; if they don't close, discard. Refrigerate the mussels until ready to use.
Melt the butter in a large saucepan or stockpot over medium heat. Add the bacon, leek, fennel, carrot and celeriac and cook, stirring occasionally, for 10 minutes, or until softened. Add the garlic and spices and cook for a further minute. Increase the heat to high, add the stock and Akvavit and bring to the boil. Cook for 5 minutes.
Add the mussels to the pan, cover, and cook over high heat for about 5-6 minutes, shaking the pan occasionally. Discard any mussels that do not open. Add half the reserved fennel fronds and season, to taste. Spoon the mussels and broth into deep bowls and garnish with the remaining fennel fronds. Serve with a dollop of crème fraîche and some crusty or rye bread, if desired, for mopping up the juices. And don't forget the shots of Akvavit!
Recipe from Snowflakes And Schnapps, by Jane Lawson, publish by Murdoch Books, £25.