In a large mixing bowl, add bread flour, sugar, salt, active dry yeast, condensed milk, egg, and milk.
Use a hand mixer with a dough hook or you can also hand knead the dough, knead the dough until it becomes smooth.
Add 10g of butter and knead until it becomes a smooth dough again.
Cover and leave at a warm place for first proof for around 45-60 mins or until the dough doubles in size.
While waiting for the bread to rise, prepare the butter layer. Fold a 10 x 10 cm area on baking paper, it is for wrapping the butter.
Cut the 60g butter into thin slices, and fill the 10 x 10 cm area. Cover it, and use a rolling pin to flatten and spread to all the corners. Leave it in the freezer until ready to use later.
Brush the muffin tins with butter. We will make 6 in total, so brush 6 muffin spaces.
When the dough is ready, take it out from the bowl, and flatten it to a square around 18 x 18cm. (It doesn't have to be accurate, as long as you can wrap the 10 x 10 cm butter in it.)
Put the butter on top of the dough, and wrap it with the dough. Use the rolling pin to press it down, then roll it out to a rectangle. Roughly divide it into 3 parts, fold the outer parts towards the middle. Repeat this folding step 3 times - flatten to a big rectangle and fold it. Tips: Whenever the dough is bouncing back when you try to stretch it, you need to rest the dough - wrap it up and put it in the freezer for 15 mins. You can also do it every time after you fold the dough.
