Start by washing your chosen berries thoroughly. If you’re using strawberries, slice them roughly to help them break down more easily during the cooking process. Place all the berries into a large saucepan.

Add the sugar, lemon juice, vanilla extract, and a pinch of sea salt to the saucepan with the berries. The lemon juice and sugar are essential for achieving the right balance of sweetness and acidity. Gently stir the mixture until everything is well combined.

Turn the heat to medium-high and bring the berry mixture to a rolling boil. Once boiling, reduce the heat to medium and allow it to boil gently. Make sure to stir frequently over the next 20 minutes.

To test if your jam has thickened, you can use a simple freezer trick. Before you start cooking, place a couple of spoons or small ramekins in the freezer. After 20 minutes of cooking, take one out and drop a spoonful of the jam on its back. If it sets slightly and doesn’t run off the spoon, you’re ready to jar it up. If it’s still runny, continue cooking, testing every five minutes until you reach the desired thickness.

Once you’ve achieved the perfect consistency, let the jam cool slightly. You can spread it on warm toast right away or let it cool completely before transferring it to clean glass jars with fitted lids. Store your homemade berry jam in the refrigerator for up to two weeks.