Add all ingredients to a cocktail shaker half-filled with ice cubes - if you don't have a cocktail shaker, you can use a mason jar or other jar with a tight lid
Shake well 20 to 30 seconds
Pour into a martini glass and add an extra dash of simple syrup if you like a sweeter drink
To create a thick crema on top, you can use a cold brew coffee concentrate, an aerolatte device, or a milk frother to gentle foam the top layer of the beverage before pouring into the glass.
Notes
If you're using cold brew concentrate, place a few drops of it on one side of the glass than slowly fill the glass with the martini.
Keyword coffee cocktails, coffee drinks, espresso, espresso martini