Meanwhile, heat 3 x 350g packs of frozen raspberries in a jam pan, until defrosted & juicy.
Add the warm sugar & heat until dissolved, stirring all the time, to avoid fruit sticking & burning at the bottom of the pan
Bring the fruit to the boil & cook for 5 mins until it shows a jam set on a thermometer, (alternatively, put a teaspoonful of jam on a cold saucer, put it in the fridge for a few minutes, then check to see if it wrinkles when the surface is touched.) Take the jam off the heat while testing, so it doesn't overcook.
Pour it into warmed jamjars, cover with greaseproof discs & lids.
Voila! Simple & delicious!