In a saucepan, combine 1 quart of the milk with the sugar and cook over low heat, stirring frequently, until mixture turns golden.
In the remaining quart of milk, stir in the soda and place in another saucepan.
Add the cinnamon stick and bring to boil.
Discard the cinnamon and add the hot milk very gradually to the caramel mixture, stirring constantly.
When all the milk is incorporated, place over a low heat and cook very slowly until the mixture is thick like melted caramel.
Cool slightly; then pour into a glass container and chill.
Please note that the cooking times and yield are approximate.