Find a saucepan, a wooden spoon, a hand whisk, and a small bowl.
Measure the sugar and water into a saucepan. Place over a low heat and stir until the sugar has dissolved. Bring up to the boil, simmer for 1 minute and then draw the pan off the heat.
Add the cocoa powder all at once and whisk until the sauce is smooth. Pour into a small bowl and allow the sauce to cool, stirring