Warm the base. Add the milk, cream, sugar, and salt to a small saucepan.
Set over low to medium-low heat. You want gentle steam, not a simmer.
Stir until dissolved. Whisk slowly for 3–5 minutes, just until the sugar melts and the mixture is warm. Avoid boiling—high heat can change the texture.
Add vanilla. Remove the pan from heat.
Stir in the vanilla extract (and vanilla bean paste if using). If you’re using a split vanilla bean, add the seeds and pod during warming, then remove the pod now.
Taste and adjust. Sample a spoonful. Add another tablespoon of sugar if you want it sweeter, or another pinch of salt to brighten the flavor.
Cool and bottle. Let the creamer cool to room temperature.
Pour into a clean glass jar or bottle with a tight lid.
Chill. Refrigerate for at least 2 hours to let the flavors settle and the texture thicken slightly.
Use. Shake well before each use, then add 1–2 tablespoons to hot or iced coffee. Adjust to taste.