A Seasonal Twist on Kosho: Fermenting with Rhubarb, Gooseberries & Plums

Kosho is a bold and spicy Japanese condiment traditionally made with fresh chilies, salt, and yuzu—a fragrant citrus fruit that adds an irresistible tang. But, as yuzu isn't readily available outside Japan, what if we swapped yuzu for seasonal fruits that naturally bring a touch of acidity? Enter rhubarb, gooseberries, and plums—ingredients that not only add a unique depth of flavour but also make this ferment more accessible year-round.

My Secret to a Thick & Flavourful Kosho?

One of the biggest challenges with using juicy fruits in fermentation is excess water, which can lead to a thinner, less concentrated result. My secret? Dehydrating the fruit slightly before fermenting.

I got this idea after experimenting with Kirsten Shockey’s recipe for daikon/mooli achar, where she partially dehydrates the radish before fermenting. This not only reduces water content but also intensifies the vegetable’s natural flavours. Inspired by this technique, I swapped out mooli for carrots in the recipe, and the result was phenomenal.

When rhubarb season arrived, I decided to apply this method to a kosho-style ferment. The result was a game-changer—so much so that a local restaurant asked me to make a version using plums for their menu. They served it with duck, and it was a perfect match. The plums added a deep, rich sweetness that balanced the heat of the chilies beautifully. Pictured is the plum kosho, made from a friend's windfall harvest after a storm toppled their tree.

How to Make Seasonal Fruit Kosho

This recipe is adaptable to different tangy fruits, so feel free to experiment. I’d love to hear if you try it with other varieties!

Ingredients:

• 500g Plums – Dehydrate for 10 hours at around 60°C (or longer at a lower temp). Higher temps will destroy microbes, but we'll get those from the fresh ingredients.

• 250g Garlic – Yes, there’s a lot to peel, so put on your favourite podcast!

• 70g Fresh Chillies – Remove the seeds. Adjust heat level to taste. (wear gloves if you can!)

• 75g Salt – Aim for 8-10% salt by weight.

Instructions:

1. Pulse the garlic and chillies in a food processor until finely chopped.

2. Add the plums and pulse again, keeping some texture.

3. Pack the mixture into a sterilized 1-liter kilner jar, ensuring there are no air bubbles.

4. Ferment at room temperature for 4-6 weeks, if it's not kilner - burp the jar as needed. It'll last in the fridge for months. Mine is about 18m old and it's better than ever!

How to Enjoy Your Kosho

This is so incredibly delicious it'll become one of your go-to condiments! Try it:

• As a topping for sushi or Japanese-style rice bowls

• Alongside barbecued meats or grilled vegetables

• Paired with duck, as served by a fancy restaurant I made it for!

I’d love to hear how you serve yours—drop a comment and share your experiments!