The principle of dough fermentation method is to leave a piece of dough when making fermented pasta the day before, let it ferment, and knead it in new materials the next day, so that it can be fermented without yeast. This overnight fermented dough is called "old noodles", also called "flour fat" and "screwdriver". In the past, yeast fermentation was used because yeast was difficult to obtain or unwilling to put yeast. There are still many people who like to use this method, because the pasta it makes is delicate and mellow, which is better than ordinary fermented products. Materials: low gluten flour 150g, medium gluten flour 50g, dry yeast 2g, salt 0.5g, ice water 100ML (warm water in winter). Practice: add water to all the dry materials and stir them into dough, and knead them until the dough surface is smooth (about 5- 10 minutes). Put the dough in a large bowl, cover it with plastic wrap and let it ferment to twice its size, about 45~50 minutes (the fermentation time will be prolonged in cold weather, so it can be kept warm in a microwave oven).