Combine the espresso, vodka, simple syrup, and amaretto in a martini shaker. Fill the shaker with ice. Shake for about 10 seconds. Divide between the chilled martini glasses. Serve immediately.
In a saucepan combine water and sugar over medium heat. Bring to a boil, reduce heat and simmer for 5 minutes, until the sugar has dissolved. Take the pan off the heat and cool the syrup. Any extra cooled syrup can be saved in an airtight container in the refrigerator.