Combine whiskey, simple syrup, lemon juice, and egg white in a cocktail shaker and dry shake. (Dry shaking means you don't include the ice. Use of a ball whisk or Hawthorne strainer spring can help.)
Add ice and shake until chilled.
Double strain into a coupe glass.
Notes
If garnishing with bitters or bitter stencil, wait for the foam to settle before garnishing.* Consuming raw or undercooked meats, poultry, seafood, shellfish, or eggs may increase your risk of foodborne illness.