Preheat slow cooker for 15-20 minutes on high. Grease the slow cooker bowl with some butter.
In a separate bowl, add Caster Sugar (1 cup), Self-Rising Flour (1 1/2 cup), Melted Butter (90 gram), Vanilla Extract (1 teaspoon), Unsweetened Cocoa Powder (2 tablespoon), Egg (1), Milk (3/4 cup), and Brown Sugar (1 cup). Mix or whisk well together.
Add mixture to the slow cooker, then dust Brown Sugar (1 tablespoon) and Unsweetened Cocoa Powder (2 tablespoon) over mixture.
Using a spoon, gently and evenly pour the Water (2 cup) over the mixture.
Cook on high for 2 1/2 hours, or until the center is firm.
Serve with Ice Cream (to taste). Enjoy!