Place the water and sugar in a large saucepan.
Simmer for 5 to 10 minutes over medium to high heat until all the sugar has dissolved, making a syrup.
Add the coffee and give the mixture a quick whisk until all the powder has dissolved.
Remove from the heat and allow to cool completely before stirring in the vodka (this last part is important as you don’t want any of the alcohol to evaporate).
Pour into sterilised jars or bottles then leave for at least two weeks to allow the flavours to mellow; the longer the better! At this point it is worth giving it a little taste and deciding if you would like to make it any sweeter. Add caster sugar in 100g increments, shaking thoroughly and leaving it for a couple of days in between additions; “you can always add extra sugar but you can’t take it out” as my grandmother would say.
Strain through a coffee filter or muslin to get rid of any cloudiness or fine grounds from the coffee powder, then decant into pretty glass bottles and label ready to give as gifts.
Once you are happy with the recipe in terms of sweetness, it is a great one to play with; add 50g of cocoa to the initial syrup to make a mocha liqueur, or swap some of the vodka for spiced rum or brandy for more complex flavours.