combine the cream, vanilla essence and sugar. Bring to a boil on medium heat stirring occasionally.
Add the lemon and yuzu juice and stir well. Bring back to a boil and remove from the heat.
Let the mixture sit for at least 5 minutes and then strain through a fine sieve into a jug.
Pour ⅔ cups per glass and refrigerate for at least 3 hours or best to leave it overnight.
With a hand blender beat the butter and brown sugar until well combined. add the flour and oats and keep mixing for 1-2 minutes.
Spread the mixture on a baking sheet or baking paper. Bake in a pre-heated oven at 180°C (350°F) for 15-20 minutes or until golden brown.
For garnishing the posset, add the crumble on the top and garnish with white chocolate shavings.