Water in a deep saucepan bring to a boil. Water should be enough to top the pan you could put the colander so that it does not spill water. (Better to try). So, as the water boils, reduce the heat, on top of the pan to put in a colander and put in a frozen berry mix.

In the process of heating on a few berries are beginning to unfreeze and give juice. They need to be stirred with a spoon and push to the juice fell into the water in a saucepan. Gradually add the sugar and grind with him berries.

So continue until the water will turn bright red rich color, and the berries will not be all (or nearly all) the juice. It will be seen - remains the so-called cake. The colander with the remnants of the berries to remove. With Morse a sample - it is likely to be concentrated, then dilute it with boiling water, add sugar to taste and bring to boil. Drain, and our morsik ready!

To be honest, I'm really sorry to throw berry remains... I add sugar and use as a filling in layer cakes or pancakes (today, exactly)