Begin by whisking together the egg yolk and the caster sugar until pale, thick and creamy.

Next, heat the milk and cream together in a heavy bottomed saucepan.

When the milk and cream mixture reaches boiling point, add a splash to the egg mixture and whisk.

Slowly add the remaining milk and cream mixture to the eggs whisking continuously.

Transfer the mix back to the saucepan and cook on a moderate heat until it is thick enough to coat the back of a spoon.

Leave this to cool before making the remaining components of the cocktail.

Next, add the vodka, kirsch and rhubarb to the whipping chamber of the cream whipper.

Charge the whipper with two nitrous oxide canisters and leave to sit for 60 seconds.

Keeping the cream whipper upright, release the gas.

Pour the infused vodka (discarding the rhubarb) into martini glasses (roughly 50ml per glass, or halfway up the edge of the glass.)

Rinse your cream whipper before adding the custard to the whipping chamber.

Again, charge with two nitrous oxide canisters and shake for 60 seconds.

Turn the cream whipper upside down and, gently pressing the trigger, dispense the whipped custard on to the top of the rhubarb vodka creating a second layer to the cocktail.

Top the cocktails with pink sugar or sprinkles and enjoy!