In a mixing glass, combine the sweet potato shochu, black pepper salted caramel syrup, Angostura bitters, and ash bitters.

Fill the mixing glass with ice and stir well until the mixture is well-chilled.

Strain the cocktail into a rocks glass over a large ice cube.

Express the oil of an orange peel over the drink, then drop the peel into the glass as garnish.

In a medium saucepan, combine the water and Demerara sugar. Stir over medium heat until the sugar is completely dissolved.

Add salt and Szechuan peppercorns (or freshly ground black pepper). Let the mixture simmer for about 10 minutes, allowing the flavors to infuse.

Remove from heat and allow the syrup to cool. Once cooled, strain the syrup to remove the peppercorns and transfer it to a clean bottle or jar. This syrup can be stored in the refrigerator.