Make the Soaker: In a bowl, combine whole wheat flour, salt, and milk. Stir to form a ball of dough. Cover loosely with plastic wrap and leave it at room temperature for 12 to 24 hours. If you plan to leave it longer, refrigerate it (good for up to 3 days), removing it from the fridge 2 hours before mixing the final dough.

Prepare the Biga: In a separate bowl, mix together whole wheat flour, yeast, milk, and egg until a sticky dough forms. Knead for 2 minutes with wet hands to distribute the ingredients evenly. Let it rest for 5 minutes, then knead again for 1 more minute. Cover the dough tightly with plastic wrap and refrigerate for 8 hours or up to 3 days.

Mix the Dough: Using a metal pastry scraper, chop the soaker and biga into smaller pieces (12 pieces each) and place them in a large bowl. Add the flour, salt, yeast, honey, and melted butter. Stir vigorously with a large spoon or knead by hand for 2 minutes, until all ingredients are evenly incorporated and the dough becomes soft and slightly sticky.

Knead the Dough: Transfer the dough to a floured work surface and knead for 3 to 4 minutes, incorporating as much extra flour as needed. The dough should feel soft and tacky but not sticky. Shape the dough into a ball and let it rest for 5 minutes.

Final Knead and First Rise: Knead the dough for another minute to strengthen the gluten. Form it into a ball and place it in a lightly oiled bowl, rolling it to coat in the oil. Cover loosely with plastic wrap and let rise for 45 to 60 minutes, or until the dough is about 1.25 times its original size.

Shape the Cinnamon Rolls: Lightly dust your work surface with flour and transfer the dough to it. Roll the dough into a 9-inch square, approximately 1/4-inch thick. Sprinkle the cinnamon sugar evenly over the dough, then roll it up tightly into a log. Slice the dough into 1-inch thick rolls and place them 1 inch apart on a sheet pan lined with parchment paper.

Proof the Rolls: Mist the tops of the rolls with pan spray, cover loosely with plastic wrap, and let rise at room temperature for 45 to 60 minutes, or until the rolls are nearly double in size.

Preheat the Oven and Bake: Preheat your oven to 400°F (204°C). Place the pan in the oven, lower the temperature to 350°F (177°C), and bake for 15 minutes. Rotate the pan 180 degrees and continue baking for another 10 to 15 minutes. The rolls should be golden brown and springy when pressed in the center. If they still feel doughy, continue baking.

Glaze and Serve: Once the rolls are baked, remove them from the oven and cool for 5 minutes before glazing.