2 Tablespoons Cocoa Powder
2 Tablespoons White Sugar (or to taste)
2 teaspoons (10 ml) Corn flour
Dissolve the Cocoa Powder and sugar in water in a saucepan on the stove on a low heat.
Separately, in a jug, dissolve the corn flour in 3 tablespoons of water or enough for it to be thinner than glue, a pourable consistency.
Pour the corn flour mix into the saucepan and stir continuously over a low heat so that the cocoa powder mixture thickens. Turn the heat up slightly and then remove from the heat just before boiling point.
Add the butter and stir continuously (off the heat) until it had fully dissolved in the cocoa custard.