For your information, the flour-to-water ratio for tangzhong is always 1 (bread flour) : 5 (water). For instance from the recipe shown below you can make a batch of approximately 150g tangzhong.
Ingredients: (able to make 2 loaf of bread with 350g bread flour)
25g Bread Flour
125ml Water(could be replaced by milk, juice or 50/50 water and milk)
2. Cook over medium low heat, stirring consistently with a egg whisk or wooden spoon to prevent the mixture from burning while cooking.
3. The mixture will thicken up (takes about less than 2 minutes) while cooking, so once you see “lines” appear in the mixture or it starts to form a dough. It is done.
4. Transfer the cooked dough into a clean bowl and cover with a cling wrap sticking onto the surface to prevent it from drying up.
5. Cool it completely before use. (I have tried using it while lukewarm and it works well too)
Do check up my latest recipe on Homemade Bread shown below.