Prepare coupette glasses by freezing them in a freezer. Cut a peel of zest from a washed grapefruit. Fill a stirring glass or mixing vessel with plenty of ice. Combine the Dry Gin, vermouth and yellow Chartreuse in the mixing vessel. Stir the mixture for ten seconds to chill and dilute the mixture. Fetch a frozen coupette glass from the freezer. Strain the drink into the frozen glass. Hold the grapefruit peel over the drink, the zest facing the surface. Pinch it to release the fragrant oils. Serve.