Strawberry and Rhubarb Jam

Wash the strawberries under cold running water, then remove the flower base and chop the fruit (cut the small ones in half, the large ones into quarters). Shorten the rhubarb stalks a little on both sides and peel off the skin in threads, then cut into 2 cm pieces.

Put the fruits in a large stainless steel saucepan, mix in the vanilla sugar and the preserving sugar and place the saucepan covered in the refrigerator overnight. Stir once every now and then.

On the following day, pull a couple of clean jars with screw-on lids through boiling water (so that they are germ-free) and then place them on a damp kitchen towel.

Put the pot with the jam on the stove - bring to the boil, mixing several times, and let simmer for 4 minutes. If it foams too much, add the butter and mix the contents of the pot with the hand blender (we don't like the fruit in pieces).

Then fill the jars with the jam and screw them on immediately. I think it is superfluous to turn the jars upside down - it just sticks the screw cap together, and a vacuum is created even if the filling compound gets into the jars very hot.