Add the water to a small saucepan and bring to a boil.
Stir in the stevia powder and simmer until it dissolves completely.
Remove the simple syrup from the heat and cool to room temperature.
Add the bourbon, cranberry juice, orange liqueur, and simple syrup to a lowball glass.
Add a handful of crushed ice and stir.
Top with the garnishes, and cheers!
Notes
You can make the simple syrup ahead of time! Store it in an airtight container at room temperature for up to 1 week or in the fridge for up to 2 weeks. Here's a more in-depth recipe for homemade stevia simple syrup.
Turn your simple syrup into a spiced cranberry simple syrup! Add fresh cranberries, cinnamon, and star anise to the pan with water and stevia powder. Stir and bring the mixture to a boil over medium heat for 3 minutes, stirring constantly. Then, strain the simple syrup and cool.
Top your cranberry whiskey sour with ginger beer to add some fizz. If you want a warming zing to this holiday cocktail, some muddled fresh ginger will also be perfect.