Combine all ingredients in a cocktail shaker.
Fill with ice and shake hard for 10–12 seconds until well chilled.
Double-strain into a chilled cocktail glass.
Serve without garnish, or express an orange twist over the surface and discard.
The dual-bitters combination - Angostura for warm spice and orange bitters for floral citrus depth - is the cocktail's defining signature; neither should be omitted. The Pegu Club in Rangoon served this as a sundowner to British colonial officers in the 1920s, and it became one of Harry Craddock's featured recipes in the 1930 Savoy Cocktail Book.
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