Boil the cherry juice with the jam sugar (according to the instructions of the jam sugar manufacturer) and add the Amaretto when boiling.
Do not be deceived that 150 ml are very much. By boiling it evaporates anyway largely. If you want it with a slight alcoholic note, add a shot of Amaretto after boiling. I came to the recipe after I made the Amarena cherries and had the cherry juice left over from the cherries and then boiled it up as jelly.
