Basically, jam sugar is regular sugar with added pectin. It’s the pectin that thickens the jam. Pectin is naturally present in most fruits (especially apples). When making jam, I like to use jam sugar that is less sweet. Regular jam sugar uses a ratio of 1:1 meaning that the amounts of fruit and sugar are equal. The sugar that I like to use requires a 2:1 ratio: the amount of fruit you use is twice the amount of sugar that you use. Cooking times vary as well. Therefore check the instructions on your jam sugar before you start!
The orange flavour in this jam is rather intense which I quite like. If you would like to make yours a little milder, use just one orange (both zest and juice).
When you cook the jam, the rosemary flavour will develop completely. Don’t worry when you can’t taste the rosemary before cooking your jam.
Ripe apricots are very soft so there is no need to puree them before cooking. They will soften during the cooking.