Creating Tang zhong: Whisk together 3 tbsp bread flour adn water in a pan until smooth. Cook over low heat, stirring frequently, until it thickens to a pudding-like consistency. This will take around 3-5 minutes to cook. Immediately transfer to a bowl so it does not overcook. Press plastic wrap directly onto the surface and let it cool completely.
Dough: In a mixing bowl, combine bread flour, cake flour, milk powder, sugar, salt, instant yeast, tangzhong, and warm milk. Make sure the milk stays below 130°F so it doesn’t kill the yeast (ideal range is 100–110°F).
Kneading: Using a stand mixer fitted with a dough hook, mix on low until the dough starts coming together. Add the softened butter and knead on medium speed (KitchenAid speed 4) for about 18 minutes, or until the dough passes the windowpane test.
Proofing round 1: Place the dough in a lightly greased bowl, cover, and proof for 1 hour or until doubled in size.
Turn the dough out and divide into 12 equal pieces. Shape each piece into a smooth ball. Cover and let them rest for 15 minutes so the gluten relaxes.
Prepare filling: Slice the stick of butter in half horizontally, then cut into 12 even pieces. Chill in the fridge while the dough rests.
Rolling: Roll each dough ball into a long triangular shape.
Starting at the base, gently roll outward while slightly stretching the dough to thin it out. Repeat on the other side—stretch and roll until the dough is evenly thin.
Place one piece of chilled butter at the base and roll the dough up tightly into a log. Repeat with all pieces.
Proof Round 2: Place the shaped rolls on a baking tray. Cover and proof for 30 minutes.
Preheat the oven to 400°F.
Spraying with water: Lightly mist each dough piece with water and sprinkle with flaky salt so it sticks.
Right before baking, spray them again generously to help create steam. This will help prevent the surface of the bread from drying out and it will help create a nice gloss.
Baking: Bake for 15–18 minutes, watching closely starting at 14 minutes. They should be golden brown.
Cool down: Transfer to a wire rack and brush with melted butter if desired. Let cool slightly.
Enjoy your soft, flaky, buttery salt bread!