Make the tangzhong by combining 25 grams flour and 125mL water together in a pot. Heat this on medium heat until it thickens into a paste. Allow this to cool to room temperature before using.
In a large bowl, combine together flour, salt, sugar, and yeast.
Add in the egg, milk, and tangzhong. Knead until it forms a rough dough
Add in the butter and continue to knead
Let the dough rest for ~40 minutes until doubled in size
Lightly knead the dough and separate the dough into 8 pieces. Knead each piece of dough into a ball and let rest 15 minutes.
Take a piece of dough and use a rolling pin to roll it out flat. Then roll the dough up into a log and wrap it around the sausage. Repeat this step with all 8 pieces of dough.
Let rest 45-60 minutes.
Brush the buns with an egg wash
Baker at 350F/177C for 25 minutes