grind 50g of oatmeal in to fine powder with spice grinder/food processor
mix the oatmeal with 40g sugar and 5g salt, and 125ml of milk in a pan
cook the mixture into a thick paste with low heat, stir constantly with spatula, don't let it stick to the pan.
(oat has a special protein that absorb even more water than wheat starch)
add 125ml of milk to cool it down and mix
Autolyse
make sure it's cooled enough, and add 5g of yeast. and 200g AP flour
mix until no lumps of flour
cover and let it sit for an hour (this is for autolyse, it will make the dough easier to work with and save you some kneading time)
Knead
knead until the surface is shiny smooth (it won't be as smooth as normal bread dough because of the oat particles, but it should look like a balloon if you wrap it into a ball, the surface should not tear)
add 30g soften/melted butter and incorporate into the dough (do not add butter before the kneading, it prevents gluten from forming)
cover and put in a fridge overnight (this solidifies the butter and tightens the starch and make the dough dryer to touch.)
Final Proof
divide into 9 portions (should be roughly 59g each), keep everything dusted with flour, the dough is sticky. Keep wrapping the dough into itself to form a ball, do this until you can feel some tension on the surface of the ball.
proof for 3 hours
Bake
put a bowl of water in the oven and preheat it to 350F
melt 15g of butter and brush on top of the doughs
bake for 25 minutes
Let it cool down for the bread to re-absorb the moisture