Lightly oil a glass or wooden chopping board and set it aside.
Empty the condensed milk into a medium-sized saucepan and place over low heat.
Wash the condensed milk tins with water and add the water to the saucepan, and mix well combining the water with the condensed milk.
Gradually add tablespoons of sugar and mix well to dissolve the sugar with the condensed milk.
Continue stirring the mixture and ensuring that the sugar is dissolved and the mixture will not get burned.
Add the vanilla essence and continue stirring.
In adding the vanilla extract, ensure that all of the sugar has been added and is well combined with the condensed milk.
With the milk-toffee mixture thickening, add the unsalted butter and continue stirring to combine the butter with the milk-toffee mixture.
When mixing the thickening milk-toffee mixture- it should be evident of the mixture coming off the saucepan.
Remove the heat and continue mixing the milk-toffee mixture for about 2 minutes and then carefully pour or scoop the mixture into the oil-prepared board.
Evenly spread the milk-toffee mixture on the board and let it cool for 5-10 minutes. *Remember to quickly empty the mixture from the pan, to prevent the mixture from hardening.
Once the mixture has cooled, cut the milk-toffee into desired sizes and enjoy with a black cup of coffee.