As previously written, I've been looking to bring cardamom into my Manhattan game for a while now. Bitters seemed an opportunity for a more subtle flavor injection than I got with ground cardamom. Lapis in DC uses both cardamom and Angostura for their drink so I figured I could, too.
For Trial #1, I used the two bitters in equal parts. The result was good, though the cardamom wasn't enough. So, for Trial #2, I went 2:1 in favor of the cardamom over the Angostura. Bingo. I suppose one could go all in on the cardamom but I like the interplay of the two together.
I don't feel comfortable calling my drink a Lapis Manhattan because the restaurant includes ingredients I didn't: orange peel and Scotch. Plus, I imagine their bartenders have a clever way of infusing the cardamom flavor directly from the seeds that I haven't sorted out yet. Maybe next time I go, I'll sit at the bar and watch them make it.
For now, mine is simply a Cardamom Manhattan.