Start by making the garnish by charring the onions in a hot non-stick frying pan to obtain colour (about 4-5mins) then set aside to cool.
Pour all of the ingredients into a mixing glass or jug, add cubed ice and stir for around 30 seconds to achieve the desired dilution. Strain into a chilled cocktail glass, or for extra flair pour it into a small glass bottle and sit it in an ice-filled tumbler to act as a mini ice bucket. Serve with a small liqueur or port glass on the side to pour it into.
Thread the cooled onions onto a cocktail stick and use to garnish the drink.