Put raspberries into a thick bottomed pan. This needs little crushing as raspberries break down quite easily.
Add sugar to the raspberries.
Bring to a slow boil, stirring while the sugar breaks down and melts.
Add the butter and allow to rapid boil for approximately 4 minutes. Stir.
While the jam is cooking, wash jars in warm soapy water, then place on baking sheet for around 10 minutes at 170 degrees. Take out of the oven a few minutes before you are ready to put your jam into it. The ideal conditions are to put your jam into jars when the jars are still warm,
Cover the jam jars if you plan to keep some for later, and simply keep until you need it. Once a jar is opened, make sure you refrigerate it until it is used. I used small jars and from this recipe, I filled 5 small/medium sized jars.