Mix the ingredients in a measuring cup.  Fill a cocktail shaker all the way to the top with big ice cubes.  Pour the martini ingredients into the shaker.  Gently rock the martini over the ice until frost forms on the shaker.  Pour 2/3 of the martini into a cold martini glass.  Cap the shaker and shake the ice and remaining 1/3 martini hard.  Pour the remiaining 1/3 martini into the glass and serve.

Our comments:  This comes from Justin Cox.  A martini glass hold 1/2 cup.  We like Belvedere vodka.  I use cold brew concentrate for the coffee (Starbucks French Roast).  The "hard shake" at the end is meant to break off little ice chips into the remaining 1/3 martini.