Dry shake, shake with ice, double strain, cocktail glass.
I made my first version with Green Hat gin, a local gin made in Washington, DC. I'm looking forward to experimenting with other brands. I can't imagine one could go wrong with Beefeater, here.
Half an ounce is a lot of crème de cacao, so I highly recommend using something that's pretty tasty, like Tempus Fugit's version. I have only tried one other brand of crème de cacao (Dekuyper) and the experience scarred me for life. Tempus Fugit's version is wonderful.
This was my attempt to come up with some uses for the two bottles of crème yvette I own. Most classic crème yvette cocktails reference the color blue in their name, since crème yvette used to have artificial coloring that made it similar in hue to crème de violette: aviation, eagle's dream, blue moon, submarine kiss, &c. The revived crème yvette doesn't use artificial coloring (not a decision I agree with), and I'll be damned if I'm going to serve someone a pink aviation.