Heat 1 cup of milk or water in a small saucepan or microwave until hot, not boiling
Add 1 to 2 tablespoons of cocoa powder to a mug
Add 1 to 2 tablespoons of sugar, if desired
Add a small pinch of salt
Pour in a few tablespoons of the hot liquid
Whisk or stir until the cocoa powder forms a smooth paste
Add the remaining hot liquid
Stir well until fully combined
Add vanilla extract, if desired
Top with whipped cream or marshmallows, if desired