This water-roux starter is the secret ingredient to creating super soft bread that lasts for days without adding any unhealthy additives or conditioners. To create this, do the following:
1/3 cup bread flour
1 cup water
The ingredients will always have a weight ratio of 1:5. I like using the designated amounts above because it is easy to remember. Mix the ingredients in a pot and heat up. Keep mixing the lumps away. Once the mixture reaches 65 deg C, it will quickly get the the point where the mixture thickens up and you should be able to create indentations that will stay as shown in the image. You can eye-ball this or use a cooking thermometer to check. Take the pot off the heat and let it cool. Store it in the fridge overnight with a piece of saran wrap directly on top to avoid drying out. The tang zhong will be good for about 3 days, but make a new batch if it turns grey.
This method was first published by Yvonne Chen's in Bread Doctor. For more information, check out the book here