Let sit at least 15 minutes, stirring occasionally.
Making the Tangzhong
Place 43 grams high fat non dairy milk (3 T), 43 grams water (3T) and 14 grams bread flour (2T) in a small saucepan.
Whisk thoroughly but do not worry too much if a few flour lumps remain.
Heat over low to medium heat whisking constantly
Stir until the flour gelatinizes and forms a paste. Your whisk should leave clear streaks in the bottom of the pan. On my gas stove this takes just about 2 minutes. If you have an electric stove, it may take up to 5 minutes.
Place the tangzhong in a small bowl to cool.
Making the dough
If you are using a bread machine, be sure to place the ingredients in the pan in the order specified by the manufacturer. This is essential for success.
If you are using a stand mixer or mixing the dough by hand, combine the non dairy milk, oil, sugar, salt, tangzhong and egg substitute in the mixing bowl.
Using a dough hook or a sturdy spoon, mix to combine.
Add the flour, potato flour and yeast. Knead on medium low speed until a smooth elastic dough forms - about 5-10 minutes. If kneading by hand it will take longer.
The dough should be a little sticky but hold together around your dough hook. If the dough is not soft, but rather stiff and is not at all sticky, add another tablespoon of milk. If it is not coming together but is messy all over the side of the mixing bowl - not just at the bottom- add another tablespoon of flour. Be patient and give it a few minutes to come together.
When your dough is complete, let it rest covered for 60-90 minutes. It will be puffy but it may or may not double in bulk.
Shaping the Dough
Place the dough on a floured surface.
To make traditional Japanese milk bread (Hokkaido), divide into four equal pieces. They should weigh 160-170 grams each.
On a very lightly floured surface, roll out one piece of dough into a rectangle about 8 inches by 5 inches.
Fold the dough like a letter - one third into the middle and the other side over the first and set aside. Repeat with the remaining three pieces of dough.
Take the first piece of dough and on a lightly floured surface roll into a rectangle smaller than the first - about 3 x 6 inches.
Starting with a short end, roll up the dough. Repeat with the remaining three pieces of dough.
Place the dough into a lightly greased bread pan. Cover with plastic wrap and let sit at room temperature for 20 minutes.
Preheat oven to 350 degrees.
Set a timer for another 20 minutes. After 20 minutes, see if the dough has risen up to the edge of the pan. If so, it is ready to bake. If not, wait 10 more minutes.
Baking the Bread
Bake in a 350 degree oven for 20 minutes.
Turn the loaf pan 180 degrees and tent it with aluminum foil to prevent it getting too brown. If you are using aquafaba, the dough tends to brown more quickly so tent after 15 minutes.
After 10 more minutes (30 minutes total) the bread should be brown and register at least 190 when a digital thermometer is inserted in the middle.
Take off the foil, take the bread out of the oven and place on a cooling rack.
After 5-10 minutes, run a knife around the edge of the pan to loosen and remove from pan. Place on rack to cook completely.
Enjoy!
Store well wrapped on the counter for up to 5 days. Freeze for longer storage.
Notes
* If you use a low fat milk alternative (like oat) use 4 tablespoons oil instead of 3
** Use either ground flax seed + water or 3 tablespoons aquafaba (not both). See article for more information
*** Potato flour - you can use a starch like tapioca but the shelf life may not be quite as long. See article for more information.