Homemade tomato ketchup

Method

1. Put the onions, celery, tomatoes, garlic, vinegar and 100ml water in a large saucepan over a medium heat. Cook for about 40 minutes, stirring occasionally, until the vegetables have completely broken down into a pulp.
2. Meanwhile, pinch the balls out of the cloves, then crush in a pestle and mortar with the peppercorns, coriander seeds, chilli flakes and celery salt. Tip into the pan as soon as you’re done.
3. Using a stick blender or food processor, whizz the cooked ketchup mixture until smooth. Press the tomato pulp through a sieve (or see tips) into a clean pan, making sure you have extracted all of the pulp, leaving behind only any seeds and tomato skins that haven’t broken down.
4. Add the sugar and set over a medium heat. Bring to the boil, stirring occasionally to dissolve the sugar. Reduce to a simmer and cook until thickened and reduced to a thick consistency (about 20 minutes).
5. Remove from the heat and season well with salt. Pour the ketchup into a jug, then use a funnel to transfer it into sterilised bottles or jars. Seal immediately and cool completely. Keep in the fridge for up to 2 weeks or, to keep for longer, put the sealed jars in a large pan of water and bring to a simmer. Cook gently for 45 minutes, then leave to cool in the water – they’ll then last up to 6 months in a cool dark place. Once opened, eat within 2 weeks and keep in the fridge.