Prepare raspberry syrup. Pour raspberries into a saucepan. Add sugar. First, mash the berries with a spoon, then use an immersion blender. The mass should be liquid but homogeneous, without taking into account the seeds.
Prepare the thickener. Pour 100 ml of raspberry syrup into a separate glass or ladle. Add 10 g of agar-agar. Stir and leave to cool.
Cook the raspberry jam. Put the saucepan with the remaining syrup on the fire. Bring to a boil, stirring all the time. If foam forms, remove it. Cook for 5 minutes. Then add 100 ml of water to the glass or ladle with the syrup and agar-agar, mix thoroughly and pour into the boiling syrup. Cook, stirring constantly, for another 5 minutes.
Close the raspberry jam. Pour the hot jam into a jar. Close the lid tightly. Leave to cool at room temperature. The jam will be liquid, but over time it will begin to thicken. When it has completely cooled, you can put it in a cool place.