Gardening takes a good deal of time and energy so you really don’t want to be wasting what you grow. Unfortunately, New Zealand weather can be particularly fickle and is often the cause of fruit and vegetables running to seed, producing a glut or failing to mature. That’s why I’m always over-the-moon when I find new ways to use produce regardless of how it’s faring in the garden.

A few years ago, while in Greece, I discovered how to turn immature citrus fruit and figs into delicious preserves called ‘spoon sweets’. This was good news for someone who lives in the south of the South Island where these fruits usually fail to ripen. Currently, I’m travelling through Iran and have encountered a popular use for another immature fruit – green grapes.

I discovered these tiny grapes (each no larger than my small finger nail and forming miniature bunches) in a fruit and vegetable market in Iran’s second largest city of Shiraz. When I was kindly offered a grape to taste, it was all I could do not to wince at its sourness. What on earth the locals did with these nasty little things was beyond me until I arrived back home and quizzed the family I am staying with.

Meheri, my host, disappeared into the her pantry and returned with a bottle of pale green liquid which had separated into two parts: a thin substance topped with a gluggy white solution. She shook the bottle up and poured me a taste. It was for all the world like lemon juice but somehow less astringent.

This liquid, which in New Zealand goes under the name ‘verjuice’, is an Iranian staple and most homes produce their own by grinding the grapes in a blender or feeding them into a juicer (if using a blender, the mixture can be sieved which does away with the thick pulp that separates from the liquid).

To preserve the ghoreh (pronounced ‘gorga’), as it is called in the Persian language of Iran, the liquid is poured into a non-reactive pan, has salt added to it, and is brought to the boil. It is simmered only for a minute before being removed from the heat. Once cool, it can be poured into sterilized bottles, and sealed. Unless you’re using a water bath method to preserve the liquid, be sure to store your ghoreh in the fridge where it should keep for several months. Or freeze it to increase its freshness and shelf life.

Ghoreh is used in cooking where a sourness more mild than lemon or vinegar is called for. It’s typically found in khoresh (Persian stews) and thick soups such as abghusht, tas kabob and ash, from the same cuisine.

From not wanting to look at my grapevine (which tends to shiver in a southern summer even when grown in a glasshouse), I now find myself eagerly awaiting a few green bunches next season. But even if you’re in a warmer part of the country where your grape vine grows delicious sweet fruit, the existence of ghoreh means you can thin without that nasty feeling you’re wasting the immature fruit. So don’t wait for a trip to Iran (which, by the way, I am pleased to recommend) before making your own verjuice, ghoreh or ‘sour grapes’ juice. Whatever you decide to call it, it will enhance your cooking in the most delightful way.