Best-ever strawberry jam

Sterilise 3 x 300g jars (or the equivalent) according to the instructions online at waitrose.com/howtosterilisejars. Put the sugar, lemon zest and juice, and strawberries in a large heavy-based saucepan and set aside to macerate for 30 minutes-1 hour.

Put 2 small plates in the freezer. Put the pan of strawberries over a medium heat and bring to the boil, stirring frequently. Once the fruit reaches a rolling boil and begins to break down, increase the heat to high and cook for 20-25 minutes until ⅓ of the liquid has evaporated and the jam reaches setting point (105ºC on a sugar thermometer). Take the pan off the heat, put a small spoonful of jam on one of the plates from the freezer and freeze for a couple of minutes. Use your finger to push the jam on the plate – it should wrinkle. If not, continue to bubble the jam for a couple of minutes, then test again.

Once ready, transfer to the sterilised jars and seal while still hot. Store sealed in a cool, dry place for up to 6 months, refrigerate after opening and use within 1 month.