The strawberries and nectarines are washed, weighed and then cut into small pieces as desired. Then mix the fruits together with the preserving sugar in a large saucepan. The pot must be chosen so large that at least double the amount would fit in. The jam could boil over.
Now let the whole thing rest overnight. The sugar dissolves a little.
The next day, bring everything to the boil while stirring over high heat and cook for at least 5 minutes, stirring constantly.
Pour the food into the prepared jars and close, turn over and let stand upside down for about 5 minutes.