Why are my tangzhong bread doughs so wet? I've started experimenting with tangzhong bread recipes after reading about it in one of the questions here. I have been baking bread for many years.
I believe I'm doing it correctly, but I find that the doughs are very wet and sticky - like, almost like a wet muffin batter that you might pour into a muffin tin instead of the usual smooth, non-sticky mass of bread dough that I am used to.
The recipes I've tried so far are:

https://www.kingarthurbaking.com/recipes/classic-sandwich-bread-recipe
https://www.kingarthurbaking.com/recipes/soft-cinnamon-rolls-recipe
https://www.kingarthurbaking.com/recipes/pillowy-white-bread-recipe

They have all turned out OK, but only after I added a fair amount of additional flour, above and beyond what the recipe calls for.
Taking the milk bread recipe as an example:
The recipe calls for a total of 2 1/2 cups (dough) + 2 tablespoons (tangzhong) bread flour and 1/2 cup (dough) + 6 tablespoons (tangzhong) milk and water. That's a total of 2 3/8 cups flour to 7/8 cup of liquid.
The recipe calls for mixing &amp; kneading &quot;until a smooth, elastic dough forms&quot;. I use a stand mixer, and the recipe advises that this could take up to 15 minutes. So I did that, and after that time I did not have a smooth, elastic dough - I had a sticky mess at the bottom of the bowl. So I proceed to add more flour, two tablespoons at a time, until it becomes the smooth mass that I'm used to - in this case, I had to add close to another cup of flour to get it to what I believe bread dough should be.
The end result was good, but given that I've had the same experience three times with three different recipes, I have to wonder if it's something I'm doing or if there's something wrong with the recipes I'm trying (they are all from the same source, after all, so maybe there's something wrong there).
Am I doing something wrong or are the proportions off in the recipes I've tried?
I make the milk bread recipe almost every week: the proportions are not off (unless, perhaps you have an extremely humid kitchen). The usual advice to measure carefully by weight applies, of course. But I will assume your measurements are correct. Then I don't think the issue here is the tangzhong, but rather the butter content of the dough. Each of those recipes calls for at least half a stick! Because butter is liquid at warm temperatures, it can certainly lead to wet, sticky dough. I have two tips to deal with this.
During mixing and kneading: combine all the ingredients except for the butter, knead using a stand mixer until smooth, about 5 minutes. Then add the butter, unmelted, in one tablespoon chunks. Continue kneading until the butter is incorporated.
For shaping: stick the dough in the fridge for 10 minutes before shaping. Always shape on an oiled surface; do not add extra flour. If the dough ever seems too wet or greasy, return to the fridge to &quot;firm up&quot;.
Very buttery enriched doughs are quite different to work with than straight doughs. As you work with it more, you should get a good sense of the correct consistency to look for and how to manage the temperature. Should you attempt something with even more butter, like a brioche, these differences will be even more extreme.