My sister makes a mean one - so I asked her secret. So does my best friend's husband - so I asked his recipe. I've ordered them all over the country, sometimes with delicious result and sometimes not so much. At last, after many tastings and much practice, here is my recipe:
The Perfect Cosmopolitan
2 oz. vodka
1 oz. Triple Sec (or Cointreau when I'm feeling rich)
1 oz. cranberry juice
a dash of Rose's lime juice
juice from one fresh lime slice
Measure: For a single cosmo, I use a shot glass and pour the ingredients right into the shaker. Usually, however, I am making them for a group. I measure everything into a 4-cup glass measuring cup so I can use the markings on the side for my proportions. Measure the vodka, triple sec, and cranberry first. Then add the Rose's and fresh lime. PARTY TIP: Make a pitcher before the guests arrive to save time during the party.
Fair warning, these are strong. To tune them down, I add a bit more cranberry or let the ice melt in the shaker for a while, shake again, and pour.
Rim the glass (if desired): For me, the Perfect Cosmopolitan doesn't require any rimmer at all. But rimmers are pretty and add a dash more sweet to the taste. I squeeze the lime into the drink shaker (or the measuring cup) and then use the rind to wipe around the top of the glass to hold the rimmer. White sugar is standard for basic cosmos, but you can really have fun with colored sugar and other little delectables! Pour the sugar onto a small plate and dip the lime-wiped top of the glass into it. Swirl the glass in the rimmer until you get a nice even coating.
Shake: The shaking is key. I find it makes a big difference when I really shake vigorously for about 30 seconds. It's about more than just mixing the ingredients; it's getting them so cold and agitated that they're almost frothy and slushy.
Pour into rimmed glass. Garnish with a lime.
sip. savor. celebrate!