Prepare the jar for storage. As this sauce will be stored for a long time, make sure to clean the jar and dry it well. There should be no moisture inside.
Remove the skin from the garlic and lightly crush to release the flavour. Slice the ginger into 3-4 mm slices.
Cut the 1/4 of the pear or apple in half, keeping the peel and core parts - you should have 2 wedges that are 1/8 of the size of the fruit. Put the garlic, ginger and fruit into the jar.
[Tip 1] If you plan to use the sauce straight away, you can grate the garlic and fruit. But this sauce is aged, so you don't have to grate them.
Mix the liquid ingredients and the sugar well. Adjust the amount of sugar to taste. I usually add 4 tablespoons of sugar. Even if the sugar doesn't dissolve completely, it's fine.
[Tip 2] Do not heat the sauce to dissolve the sugar, as it robs the soy sauce and sake of their flavour. You just need to mix the sauce for a while.
[Tip 3] You can use any sugar you like, but the sauce tastes richer if you mix some brown sugar or honey in with the white sugar.
Pour the liquid into the jar and loosely screw on the lid. Let it age at room temperature for 10 days to 2 weeks. Mix from the bottom from time to time.
[Tip 4] The sauce has to breathe as it matures, so don't close the lid too tightly. However, if you're going to mix the sauce by shaking the bottle, make sure to screw it tight.
Once the aging process has finished, close the lid tightly and store it in the fridge. You can keep the garlic, ginger and fruits in it, but if you want the sauce to be clean, strain it.
[Tip 5] When the sauce turns clear and glossy, it's done.
There may be some garlic sediment in the sauce. When I made this in my restaurant, I used four times the ingredients and added the garlic whole, but in this recipe it's crushed.
If you prefer to make an authentic clear sauce, make this with 4 times the amount of ingredients. With that much, there's no need to crush the garlic or slice the ginger! If you like this method, make a lot, as it can keep for a long time.
[Tip 6] You can use the garlic and ginger for another dish. Just chop them up and stir-fry -- it'll be delicious. However, don't reuse the fruit.
[Tip 7] The more aged the sauce is, the more delicious it is. The best way to preserve the taste is to keep mixing in new sauce.
[Adding new sauce] Strain the sauce that you have on hand first, then add the old and new sauces to a new jar. If more than 1/5 of your sauce is properly aged, you can add it to a dish right away.
Story Behind this Recipe
When I owned a restaurant, this was my precious all-purpose secret sauce. The original recipe made a large amount and took a few months to age. But I adapted the recipe for quicker use at home. It's a great all-purpose sauce for yakiniku, stir-fry or any kinds of dishes you like.
You don't have to sterilize the jar by boiling it if the jar is clean and there's no moisture left in it. But if you prefer to sterilize it, use alcohol to do so!
Heating this sauce will destroy the fragrance and flavour. It's better to keep the alcohol from the sake and mirin, so that the sauce is fragrant and can be preserved well. Don't forget to add the fruit.