To make the ganache ahead, use a 1:2 ratio of chocolate to cream. This ration makes a particularly runny ganache, perfect for pouring and drinking. Measure 200g of double cream into a pan with vanilla essence and heat until nearly boiling. Pour over 100g of broken up dark chocolate and stir until melted and smooth, leave to cool and cover with cling film to prevent skin from forming.
To make the cocktail, add all ingredients into a shaker. Shake until thoroughly combine, add cubed ice and repeat until suitably cool. Double strain into a martini glass and garnish with a little grated chocolate. If you’d like to go a step further, you can freeze your glasses and dip the rims in melted chocolate before pouring your liquid in.