Remove leaves from strawberries and place in a bowl. Cover with the sugar and leave over night/for several hours.
Place sugar and fruit into a large pan and slowly heat the mixture up until the sugar is completely dissolved.
Make sure all the sugar is completely dissolved by stirring the jam. It should be clear and may have scum on top. Make sure there's no gritty texture when stirring.
Use a spoon and remove any scum that's formed on top of the jam.
Turn the heat up so that your jam is at a rolling boil (stirring it shouldn't pop the bubbles). Boil the jam for 5 minutes and then remove from the heat.
Add a tea spoon of jam to your cold plate. If a skin forms, the jam is ready to transfer into jars. If it doesn't for a skin, boil for a few more minutes.
Pour/ladle the jam into jars while they're still hot. Place the lids on the jar and leave to cool. The seal on the jar will be sucked downwards as the jam cools.