To begin, make the koji. If preferred, you can buy premade koji seasoning to save time – you will need 50ml for this recipe

Mix the rice koji with the salt, add the water and mix through. Place in a container

Place a lid on the container, making sure you leave a small fraction of the lid open so any gases that are produced can escape. Place in a warm area like an airing cupboard

Stir once a day for 2–3 days, then leave to ferment for 1 week to 10 days. Consume as soon as possible after this time

To make the stew, heat the oil in a large pan and sauté the onions until softened

Add the potatoes and the dashi, bring to the boil for a minute and then reduce to a simmer

Add the carrots to the saucepan and simmer for another 20 minutes

In a separate medium pan, prepare the roux. Melt the butter over a low heat. Add the flour, stir well with the butter and cook out for 2 minutes. Pour in a splash of the cold milk

Whisk until smooth, still over a low heat. Gradually whisk in the remaining milk, ensuring all of the milk is gradually absorbed to create a creamy white sauce. After 5 minutes, increase the heat until the mixture thickens and bubbles. Add 50ml of the koji seasoning

Add the roux to the stew, stir in the broccoli and mushrooms and bring to a gentle boil for a further 2–3 minutes. Check the seasoning for salt and pepper then serve immediately