Vanilla Rhubarb & Blackberries jam

We have got rhubarb and berries in huge quantity for a while, and the first thought has always been: the best way to use them is doing a jam. However, we have always been saying it and never actually DOING it!
This year, I decided to put myself in action, especially after tasting a fantastic jam made by our friend Ullis. Inspired by that jam, with rhubarb as well, I improvised this other jam.
According to the our guinea pigs, this turned out to be a success - with the exception that for cooking a jam you need to wear a protective overall and "plastify" the whole kitchen, or one will have just stains of jam everywhere (and the ones produced by berries are very very very evil indeed :-) )

Ingredients for about 1,5 kg of jam:

• 1kg of rhubarb
• 500 gr of blackberries
• 1 kg of jam sugar
• one vanilla rod
• the juice of one lemon

I mainly followed the instructions on the jam sugar package. One can use also standard sugar, but this was my first attempt to cook a jam, so I didn't want to risk. With standard sugar one needs a thermometer since you need to reach a specific temperature (104°C if I remember right).

One thing I did before following the instructions was to warm the frozen rhubarb and the berries in the same big pot that I used for cooking the jam.

Once the fruit was all warmed, I blended the fruit and then I added the juice of the lemon and the vanilla rod, previously cut opened.

I mixed everything carefully and then I added the sugar and cooked it for the time written on the package of the sugar.

I did 1,5kg of jam, but the original was for 1 kg and was supposed to have 700gr of rhubarb (300gr of berries, in that case red currants) and 1 kg of jam sugar. In this way, my result was less sweet than the original one, but I think it worked for this combination.

Before putting it in the sterilized jars (one can both boil them in water for 5 minutes or put them in the oven for 30 minutes at 100°C), I let it cool down a bit. 

Once the jars are filled, I put them in a dark, dry place to cool completely and rest.