Warm the milk and add cocoa to it. Mix well to combine, strain to remove any lumps.
Add sugar and water in a deep non-stick vessel preferably. Stir and cook on
low to medium flame until the sugar has dissolved.
Add condensed milk, stir for 2min and add cocoa milk mixture.
Cook on medium to high flame, stirring continuously. Make sure the spatula
touches the bottom and the bottom corners as you stir.
Once the mixture starts bubbling, reduce the flame and cook until the
mixture turns thick.
Add cold butter and cook until the mixture starts leaving the sides of the
pan. To know if it is of the right consistency, drop a spoonful onto a
buttered plate. Let it cool for 2 min, roll into a ball. If the mixture is coming
together into a ball, take off the flame and pour into a 7 inch buttered
square ring or metal dish or steel plate with rim.
Let it cool for 10 to 15 min, slice with a warm knife. Cool completely and
store at room temperature.