Mix ingredients: In a mixing bowl, combine the cocoa powder and sweetened condensed milk. Stir well until the mixture forms a cohesive dough. If it is still very sticky, you may need to add more cocoa powder.
125-150 g pure unsweetened cocoa powder (some more to coat), 1 can sweetened condensed milk (about 400g)
Refrigerate: Roll the dough into a 1cm thick square and cover with foil. Refrigerate it for about 1 hour to set and make it easier to shape.
Shape: Cut the dough into equal squares, it should give about 25 truffles. Dust over some cocoa powder, and shape each one by lightly pressing the edges. Cover with some more cocoa powder for the finishing touch.
Store: Store in the fridge for a couple of weeks.