750ML of your bourbon or rye whiskey of choice
2.5 oz simple syrup (1.5:1 ratio sugar/water)
40 dashes Peychaud’s bitters
40 dashes orange bitters (Fee Brothers or similar)

700g whiskey blend
115g filtered or other high quality water
150g simple syrup (1:1)
4g Angostura
2g Peychaud’s

Pour the entire measure (close to a full bottle) of whiskey into a glass container that can be shaken or vigorously stirred, along with the water. Add the simple syrup and shake/stir the mixture.

In a separate cup, combine and measure the bitters, and then combine that with the whiskey mixture. Shake again, and chill overnight in the refrigerator (do not freeze it).

To serve, shake the container to ensure there’s been no separation, and pour 2.5 ounces over a few cubes of ice.

(edit: a lot of experimentation and I’ve ended up on the updated recipe)