I have posted the story on shio-koji craz in Japan, the other day. Here is the recipe for you to make your own magic seasoning. You need 300g dry koji (you can find at Japanese food store or online), 100g sea salt and 500g tap water.
In a bowl add the dry koji and gently rub them with your hands to separate the grains. Add the salt and repeat the process. Add the water and repeat the process. When the water acquires milk color transfer the mixture to a plastic container. Leave the container, covered loosely, at room temperature for about one week (winter time; 10 days). Stir the mixture once every day. You may need to add additional 100g water on the second day or so when the koji absorbs the most water in the container. As the mixture matures the flavor changes to sharp salty flavor to mild salty flavor with sweetness. I store the matured shio-koji in the refrigerator and enjoy it for one year, if it lasts that long. Usually it disappears in 3 weeks.
I use shio-koji to marinate every protein ingredients – beef, pork, chicken, seafood and tofu, before cooking them. The digestion enzyme in shio-koji works as a tenderizer, at the same time giving wonderful flavor to the cooked items.
The other day I have marinated the boneless and skinless chicken thigh (1 pound) in the mixture of 3 tablespoons shio-koji, 2 crushed garlic cloves, 6 sprigs of lavender and 1 1/2 tablespoons olive oil for 3 hours. After gently wiping the chicken with paper towel I cooked it in the heated skillet and then in the oven. No salt and pepper is necessary when you cook the chicken. The chicken is already flavorful and it is a new flavor experience. You can pickle raw vegetables – for example, cut up carrot, cucumber, red radishes, and so on – in the shio-koji. Summer is the best time to enjoy shio-koji pickling.