1. Combine 2 cups water and 2 cups sugar in a deep pan, boil until the sugar dissolves.
2. Add plums cut in halves. The pan/pot must be big enough to hold it all. Mine is a 3-liter, works well.
3. Let simmer on low heat stirring regularly but gently, so all plums are covered in the syrup but not broken. Some will break, so don't let the perfectionist in you go bezerk.
4. When all plums have boiled for a bit, remove from heat. This can be done the day before, or whenever you have a bit of time and plums aplenty to play with.
5. For the tarragon jelly, wash and let dry the herb, chop or tear the leaves and stalks together, cutting off the rough bottom parts and any dirty or rotten leaves.
6. Put the tarragon into a small pot, add 2 cups water and citric acid (or 2 cups apple/grape vinegar) and bring to boil on low heat.
7. Add 1 cup sugar, continue simmerring until the sugar dissolves. Honey works well instead but mind the dosage.
8. Remove from heat, let cool to room temperature, then drain the syrup. throw away the leaves.
9. Going back to plums. Remove the whole and broken (if any) plums from the pot or drain the syrup. You should have about 0.5-0.7 liter of syrup depending on how juicy your plums are. Use the plums for another jam, pies or whatever, we don't need them here any more.
10. Combine the plum syrup and the tarragon syrup in one pot, taste for sweetness/acidity. If too sweet, add some lemon juice.
11. Add pectin, agar-agar or any other gellant but not gelatine! Use the instructions for the dosage on the gellant package.
12. Bring to boil on low heat stirring regularly to avoid pectin lumps. Do not boil for over 3 minutes or the gellant will break down.
13. Pour into jars, cover. Make sure the jars are filled to the brim to avoid air under the lid.