Prepare Your Jars: First, sterilise four 500ml canning jars and their lids. You can do this by running them through a hot cycle in the dishwasher or by washing them in hot, soapy water and then placing them on a baking tray in an oven preheated to 140°C (120°C fan) for at least 15 minutes. Keep them hot until you're ready to fill.

Prep the Apples: As you peel, core, and slice your apples, place them into a large bowl filled with cold water and the 60ml of lemon juice. This will stop them from browning while you prepare the rest of the ingredients.

Create the Syrup Base: In a large, heavy-bottomed saucepan or Dutch oven, whisk together the caster sugar, light brown sugar, cornflour, cinnamon, nutmeg, and salt. Breaking up any lumps now is important for a smooth syrup.

Cook the Syrup: Gradually whisk in the 750ml of cold water until the mixture is smooth. Place the pan over a medium heat and bring it to a boil, stirring constantly. Continue to cook for 2-3 minutes, until the syrup has thickened and turned glossy.

Add the Apples: Drain the apple slices well and gently add them to the hot syrup in the pan. Stir carefully to coat all the slices without breaking them.

Simmer Gently: Bring the mixture back to a gentle simmer. Cook for 5 to 8 minutes, stirring occasionally. The apples should be just tender when pierced with a knife, but still hold their shape well. What works best for me is to test a slice after 5 minutes; you want a little bit of bite left, as they will soften slightly more in the jar.

Fill the Jars: Carefully ladle the hot apple pie filling into your hot, sterilised jars, using a canning funnel to avoid spills. Be sure to leave about 2cm of headspace at the top of each jar. Run a clean spatula or chopstick around the inside of the jar to remove any air bubbles.

Seal and Process: Wipe the rims of the jars clean with a damp cloth, place the lids on top, and screw the bands on until they are "fingertip tight" – secure, but not forced. Process the jars in a boiling water bath for 20 minutes. For detailed, up-to-date safety instructions on water bath canning, please consult a trusted resource like the Food Standards Agency.

Cool and Store: After processing, use a jar lifter to carefully remove the jars from the water bath and place them on a tea towel on your worktop. Leave them undisturbed for 12-24 hours. You should hear the lids "pop" as they seal. Check the seals before storing in a cool, dark place for up to one year.