Combine the reposado tequila, mezcal and agave syrup in a mixing glass.
Add two dashes of Angostura bitters.
Add ice and stir for 25–30 seconds until well chilled.
Strain over a large clear ice cube in an old-fashioned glass.
Flame an orange twist over the surface, then drop it in.
Created by Phil Ward at Death & Co in New York in 2007 and now on menus everywhere. Ward's insight was that agave spirits do the same job as aged whiskey in an Old Fashioned — the mezcal is a seasoning, not the base, so keep it at a quarter.
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