Start by making the avocado mousse. In a small food processor, add the avocado and the crème fraiche and pulse to combine. Add the lemon juice, olive oil, salt and pulse again until smooth. Transfer to a bowl and cover with cling film directly touching the surface of the mousse. Keep in the fridge until you’re ready to serve.
In a separate small bowl, mix together the crème fraiche and horseradish. You can add more or less horseradish depending on how spicy you like it. Cover with cling film and transfer to the fridge.
Finely chop the smoked salmon and add to a bowl along with the lemon juice, zest and dill. Mix to combine.
To assemble the glasses: Add a small dollop of the horseradish cream on the bottom of each glass. Add a layer of the salmon mixture, followed by a layer of avocado mousse. Repeat with another layer of salmon and then a final layer of mousse. To finish, place a small dollop of the horseradish cream on top and decorate with a sprig of fresh dill.