Melt chocolate chips, stirring constantly, in saucepan over low heat. Stir in sugar, water and salt.
Increase heat to medium. Cook, whisking constantly, until mixture comes to a full boil. Continue cooking 2 minutes, stirring constantly.
Add milk and half & half; cook until heated through. (Do not boil.) Add vanilla.
Remove from heat; beat with whisk until frothy.
Pour into mugs. Serve with whipped cream.
If desired, sprinkle with your choice of toppings: grated chocolate, grated orange zest, ground cinnamon, or ground nutmeg.