Bring wine to a simmer over low heat . ** Heating the wine first is optional, do that only if you want to reduce the alcohol level.  If not, simply add the wine over the cocoa and milk mixture, and bring everything to a boil.

Meanwhile in a bowl combine cocoa powder with sugar and salt. Add 2 or 3 tbsp of milk and stir well to combine.  Add the rest of the milk, stir well and add over the wine. Bring to a boil while whisking from time to time.