Place the baby sorrel, lemon juice, olive oil in a food processor until finely chopped. Set aside.
Place the gelatine leaves into a bowl of cold water and soak for 10 mins.
Heat ¼ of a cup of the thickened cream in a small saucepan over medium heat. Add the softened gelatine and stir until dissolved. Set aside to cool.
Place the smoked trout and prawns into a food processor and process until finely chopped but not smooth. Transfer mixture to a large bowl. Add, lemon, dill, chives, paprika and season with salt and pepper, mix to combine.
Whip the remaining cream until soft peaks form, add the gelatine mixture and crème fraîche and combine with the prawn mixture.
Line a loaf tin with glad wrap and place cucumber ribbons overlapping, spoon in the prawn mixture and fold over the cucumber to enclose. Refrigerate for 2 hours or overnight.
To serve, upend the loaf tin onto a serving platter, remove the glad wrap and top with fresh prawns. Drizzle with sorrel sauce and sprinkle with baby sorrel and finely grated horseradish.