First make the 'crackle'. Line a small baking sheet with baking parchment.
Put the sugar and syrup in a small saucepan and stir over a very low heat until the sugar has completely dissolved. Bring to the boil and bubble until it turns a golden caramel colour. Take off the heat and stir in the bicarbonate of soda and cinnamon.
The mixture will froth up immediately, pour onto the lined baking sheet, sprinkle over the nuts, if using, and leave to cool and set. Break into rough shards.
Lightly whisk the double cream with the vanilla until it just begins to hold its shape. Fold in the crème fraîche. Mix together the Wild Blueberry Conserve and vodka.
Just before serving, layer the conserve and creme in pretty glasses and finish with shards of crackle.
The crackle can be made up to 2 days ahead and stored in an airtight container.
Mix the conserve and vodka the day before and set aside.
If you don't want to make the crackle, buy a large chocolate - covered honeycomb bar and roughly chop.