Plums are washed and cleaned from the stones. Dust with 1 kg of sugar and left overnight. On the next day, and is covering the second kilogram sugar, cocoa is added and put to boil. After boil, boil on low heat for one hour. Stir gently from time to time so as not to crush the plums. A few minutes before the end is inserted and vanilla sugar. Still hot pour into jars, sealed with cap and turn until cool.