Note to self: Gin:Grapefruit :: Ham:Eggs

I bought two gorgeous grapefruits, all dark pink and heavy, from the market for only $1.50. So now I'm thinking of some sort of grapefruit and gin cocktail. My roommates are quite fond of gin slings--they use Bombay, fresh-squeezed grapefruit juice, sweet vermouth (I think), angostura bitters, and soda water.

I think I want to try something simpler. Tanqueray, grapefruit juice, simple syrup (Demerara), and angostura. I could throw in an egg white for texture. A kind of variation on a sour, I suppose.

I also noticed a recipe that calls for gin, grapefruit juice, and maraschino liqueur. Something else to think about...

Does anyone else have favorite grapefruit cocktails?