Add the milk and sugar to a medium sized sauce pan.

Bring to a boil and then reduce to a simmer on medium-high heat, stirring continually. The milk will reduce by half its volume.  This will take about 20 minutes.  The milk can boil over any point, so keep stirring occasionally and don’t walk away.

After about 17-18 minutes, the milk will turn a warm cream color and the texture will become frothy.

Turn off the heat and add the baking soda, butter and vanilla. Stir well and let it cool.