Stir with ice, strain into stemmed cocktail glass, orange zest garnish.
I intended to post this one last December after corresponding with Stephan Berg over what I suspected were ingredient discrepancies in Difford's Guide "Amber Room No. 2." He confirmed what I anticipated the calls and garnish would have been, and revealed the name was simply "Amber Room Cocktail" not No. 2.
Don't be deterred by the vermouth. I originally made this with ambrato vermouths I had available at the time and used Regan's orange bitters before getting Bitter Truth orange. It was some months before I was able to import some NP Ambre vermouth--not presently available in the U.S. While still very good with the Noilly, the cocktail is even better with the Mancino Ambrato which has more wormwood bite than the gentle Noilly. Martini & Rossi Ambrato also works well for much of the same reason, midway between the Mancino and Noilly in profile.
Stephan Berg first created this cocktail sometime between 2000 and 2007 while tending bar in Munich (I have listed 2006 because that was when Bitter Truth launched their orange bitters which were specifically used here.)
Correspondence with Stephan Berg of Bitter Truth.