In a medium-sized bowl, whisk together the egg yolks and sugar until well blended and slightly thickened. You'll want everything to look smooth and inviting. Trust me; this sets the stage for the richness to come.

Next, in a saucepan, combine the heavy cream, whole milk, salt, and cinnamon. Heat this mixture over medium heat until it starts to steam, but don’t let it boil! Remove from heat, and slowly pour about a third of the warm milk mixture into the yolk-sugar mixture, whisking continuously to temper the eggs.

Pour the warmed egg mixture back into the saucepan with the remaining cream mixture. Cook over low heat, stirring constantly until the mixture thickens enough to coat the back of a spoon. This might take about 5-7 minutes. You'll know you're ready when you can run your finger through the custard on the spoon and see a clear line.

Remove from heat and stir in the vanilla bean paste and the bourbon or dark rum if you’re using it. These additions work wonders in elevating the flavor.

Next, transfer the custard to a clean bowl. Cover it with plastic wrap, pressing the wrap onto the surface to prevent a skin from forming. Allow this to cool at room temperature for about 30 minutes before placing it in the refrigerator for at least 4 hours or overnight. Patience pays off, folks!

Once chilled, it's time to churn! Pour the custard into your ice cream maker and churn according to the manufacturer's instructions. This usually takes around 20-25 minutes until it reaches a soft-serve consistency.

After churning, transfer the custard to an airtight container. Freeze for about 2-4 hours to firm up further. Your frozen custard will be ready to enjoy!