Place two Martini glasses in the fridge to chill.
Start by making the sugar syrup: Put the caster sugar in a small pan over a medium heat and pour in 50ml water. Stir, and bring to the boil. Then turn off the heat and allow the mixture to cool. (Or you can simply cheat and buy a ready made syrup)
Once the sugar syrup is cold, pour 1tbsp into a cocktail shaker along with a handful of ice, the vodka, espresso, and coffee liqueur.
Shake until the outside of the cocktail shaker feels ice cold.
Strain into the chilled Martini glasses (garnish with coffee beans if you want to be fancy).
Serve, and enjoy!