In the bowl of a stand mixer, combine the bread flour, sugar, instant yeast, and salt. Mix to combine.
370 g bread flour, 30 g granulated sugar, 6 g instant dry yeast, 6 g salt
Add the saffron bloom mixture, whole milk, and egg. Using the dough hook attachment, knead on low speed for about 10 minutes until a cohesive dough forms.
Bloomed saffron, 155 g whole milk, 1 large egg
Gradually add the cubed butter, one piece at a time, kneading until fully incorporated before adding the next.
65 g butter
Continue kneading for another 10–20 minutes, until the dough is smooth, glossy, and passes the windowpane test (it should stretch thin without tearing).
Once the dough is ready, remove it from the stand mixer and gently shape it into a round ball. Transfer the dough to a lightly oiled bowl, covering it with plastic wrap.
Allow the dough to rise at room temperature, or ideally at 80°F (27°C) for 1 hour, or until it has increased in size by 60%.(I know percentages can be a bit confusing—just think of 100% as the dough doubling in size, so 60% is slightly over halfway there.) Once it has risen by 60%, transfer the dough to the fridge and let it chill for 1–2 hours, or until it has fully doubled in size. The chill helps to firm up the dough, making it easier to handle when shaping the buns.