Add the dry ingredients to the bowl of a stand mixer fitted with a dough hook. Mix until everything is combined.
400 g bread flour, 50 g granulated sugar, 7 g sea salt, 7 g instant dry yeast
Add milk and egg to the dry ingredients.
200 g whole milk, 1 large egg
Knead for 10 minutes until the dough comes together.
Add cubed, softened butter, one cube at a time. When all the butter is added, scrape down the sides of your bowl, and continue kneading for 10-20 minutes until the dough passes the window-pane test.
70 g unsalted butter
Place the dough on your work surface and roughly pre-shape the dough into a round using your hands and a bench knife.
Transfer the dough to a clean, lightly oiled bowl, cover, and place in a warm spot, ideally at 78°F/26°C.
Proof the dough for 1 ½-2 hours or until doubled in size.
Meanwhile, make the Cinnamon Sugar Filling: