In a large saucepan, combine the butter and sweeteners. When the butter has melted, whisk to combine well. Bring to a boil and cook 3 to 5 minutes, being careful not to burn it.
Remove from heat and stir in the vanilla and salt. Sprinkle the surface with the xanthan gum and whisk vigorously to combine.
Slowly add the cream, whisking constantly; the mixture may bubble vigorously. Stir in the almond milk. Set over medium low heat and cook, whisking frequently, until the mixture reaches 165F on an instant read thermometer.
In a medium bowl, whisk the egg yolks until smooth. Slowly add about 1 cup of the hot cream mixture, whisking constantly. Then slowly return the egg yolks to the hot cream in saucepan, whisking constantly. Continue to cook until mixture reaches 175F on an instant read thermometer.
Pour the custard into the bowl set over ice bath and cool 10 minutes. Then wrap tightly in plastic wrap and chill at least 2 hours.
Whisk in the vodka, if using. Pour the mixture into the canister of an ice cream maker and churn according to manufacturer's directions.
Once churned, transfer the ice cream to an airtight container. Freeze until firm, about 2 hours.