Ensslin's customers back in the day musta been tough guys; 2 dashes Grand Marnier? Maybe I have "brut" oloroso, but even with Difford's 1/2 oz orange liqueur this is barely sweet enough. Great flavors, though; a nice, simple yet complex Manhattan variant. Use a big orange zest. Be interesting to try with Lustau East India Solera sherry, might have been more like what Ensslin used.