Strain into a double rocks glass over 1 large ice cube.
3.
Garnish with an orange twist and a lemon twist.
Notes
On the base spirit
Bourbon is generally sweeter than the popular alternative (rye whiskey), but rye is a perfectly suitable option. Rittenhouse, Minor Case, and Elijah Craig are excellent.
On the sweetener
Death & Co calls for a 2:1 rich demerara syrup, but a 1:1 demerara (linked in the recipe) or plain simple syrup are also suitable. Another well-known option is to muddle a sugar cube with the bitters; however, I've found the sugar doesn't fully dissolve this way and leaves an unpleasant grittiness in the drink.