For the cream: whisk together the egg yolks and the sugar until the mixture turns white and fluffy.
Add the chestnut cream and mix well.
In a separate bowl, whip the double cream until thick and then gently fold in the Greek yogurt.
Add the chestnut mixture to the Greek yogurt and the cream mixture and gently fold together.
To assemble the dessert: mix the coffee with 30g sugar and the cognac.
Dip the biscuits into the coffee and then place in the bottom of your glasses. Top with a layer of the cream and then a sprinkle of cocoa powder.
Repeat this until you glasses are full. Finish with a layer of cream and a dusting of cocoa powder.
«To vary the flavour of the the tiramisu add fresh orange zest to the cream rather than the chestnut puree.»