Photograph: Karen Thomas
Line a small baking tray with a double layer of clingfilm. Lay the salmon on it, skin-side down, and pour over the gin.
In a small bowl, mix together half the dill, the juniper berries, sugar, salt and pepper, then spread thickly over the salmon to cover completely. Wrap tightly in the clingfilm, cover with another baking tray or a small chopping board and weigh down – two tins work well. Chill for 2-4 days to cure, turning once a day.
To serve, scrape off the curing mixture from the salmon fillet and discard. Pat the salmon dry with kitchen paper and sprinkle the top side with the rest of the chopped dill. Slice into 36 small pieces.
For the slaw, mix the vinegar and sugar in a bowl. Discard the outer leaves of the fennel and cut lengthways into wafer-thin slices. Trim off the ends of the asparagus and cut the spears into diagonal slices. Top and tail the radishes and slice them into thin discs, then into fine strips. Add all the vegetables to the vinegar mixture and toss together to coat.
Divide the salmon pieces among the biscuits, arrange a little slaw on the top of each and serve.
Get ahead: prepare the salmon up to 4 days in advance. Slice the vegetables for the slaw a few hours ahead; chill, but don't add the dressing until just before assembling.
Kitchen secret: if you're short of time, omit the first three steps and use 2 x 180g packs of smoked salmon – just sprinkle with 2 tablespoons of gin and toss with the chopped dill before slicing into smaller pieces.