This is my espresso martini recipe.       1 oz cold espresso  1 1/2 oz vodka  1 1/2 oz Kahlua  1 oz creme de cacao    I make the espresso fresh and let it cool for about 15 minutes.   After mixing, I pour it into a martini glass with crushed ice.   For ease, sometimes, I do one part of each ingredient and that works well too.