Add the sugar into a saucepan over low heat, stir until it melts, as soon as it melts, gradually add the water. Keep stirring, and as soon as it turns into caramel, turn off the heat.
Transfer all the caramel to a silicone mold and set aside.
Then, into another pan, add the condensed milk and the corn starch, mix very well until combined. Add the milk, the butter or margarine, turn on the heat and mix nonstop until a smooth and consistent cream is formed.
Turn off the heat and transfer all this cream to the mold we've set aside, spread the cream very well.
Let it rest for 30 minutes then put it in the fridge and let it chill for 3 to 4 hours.
Unmold and serve.