Fill a martini glass with large ice cubes.  Fill the martini glass to the rim with Vermouth.  Allow to sit while you prepare the gin (for about 5 minutes) to chill the glass and the Vermouth. 

 

Fill a cocktail shaker all the way to the top with big ice cubes.  Pour the gin into the shaker.  Gently rock the gin over the ice until frost forms on the shaker.  Dump the martini glass with the Vermouth and ice into the sink.  Immediately pour 2/3 of the gin into the cold martini glass with the leftover Vermouth residue.  Cap the shaker and shake the ice and remaining 1/3 gin hard.  Pour the remiaining 1/3 martini into the glass, drop in a single olive and serve.

 

Our comments:  This comes from Darryl Rawlings.  My martini glasses hold a 1/2 cup.  The "hard shake" at the end is meant to break off little ice chips into the remaining 1/3 gin.