Put the sake lees and soy milk in a saucepan and mix well. This is easier if you bring them to room temperature first.
Reduce to low heat to evaporate the alcohol from the sake lees. Keep mixing it to prevent it from burning. If you have garlic, add it here.
Add salt, pepper and miso to adjust the taste, and it's done.
If you want to make a small amount, put smaller quantities of the ingredients into a heatproof dish, and microwave at 200W (low setting).
Story Behind this Recipe
The amount of sake lees to use should be about half the amount of soy milk. Also, adding the sake lees to shop-bought white sauce makes it even richer. Although it's useful to use a blender when mixing, it's a hassle to wash up, isn't it? I mix the ingredients little by little with a spatula and ladle.
Although I recommend using white miso (for colour), you could also use combined or barley miso! You could also leave out the miso, but the sauce will not be quite as thick. You could make gratin by pouring the sauce over fried onions or potatoes. If you use more miso and add soy sauce, it will make a Japanese-style sauce for foil baking.