Clean and remove the ends of the courgettes. If large, slice in half lengthways and then into half moons around 1/2cm/1/4" thick, or slice into rounds if smaller.
Pack the courgette slices into a large jar (or 2 smaller ones) along with the garlic and dill. Alternating the layers.
Dry fry the coriander seeds, peppercorns and chilli flakes in a small frying pan until fragrant. Grind them in a spice grinder or pestle and mortar and tip the mix into the jar(s).
Pour the sugar into the same frying pan, add a pinch of salt, and 3 tablespoons of water. Cook over a low heat until the sugar has dissolved, remove from the heat and add the vinegar.
Pour the liquid over the courgettes in the jar(s), mix well and allow to cool.
The pickled courgette can be served after they have been chilled for an hour, but the flavour will only improve with time, so they are best left for a couple of weeks. Left in the fridge, they should be good for up 3 months.
Notes
The courgette chutney should be stored in a cool, dark place for 3-4 weeks before eating.
Once opened, keep in the fridge and use within a couple of months.
Stored in a cool, dark place, the jars of sealed chutney will keep for a year.