In a large pot whisk together the sugar and cocoa, then add the milk and cream combine well.
When the mixture it is well combined place the pot over medium heat, stirring continuously, bring to a boil and slow boil for 5 minutes, whisking often.
Remove from heat and let cool. Once it is cool add the vodka and mix to combine completely. Pour into a bottle and refrigerate until really cold, about three hours, shake well before serving. Delicious served over ice too.
Will last up to a month in the fridge, shake well before serving.