Preparation

1. Put the flour, yeast, and salt into the bowl of a stand mixer. Whisk well to combine with a hand whisk or the whisk attachment of the mixer. Attach the dough hook to the mixer. Add the milk, eggs, honey, and vanilla to the dry ingredients. Start kneading on Speed 1 and gradually increase to Speed 3. Continue kneading until the dough comes together, stopping to scrape down the bowl as necessary.
2. While the dough is kneading, add the butter, one cube at a time, until all is incorporated. Continue to knead until the dough is soft, springs back to the touch, and pulls away from the sides of the bowl. If it is too sticky, add flour, 1 tablespoon at a time. This should not require more than 4 tablespoons of flour. The entire kneading process could take up to 12 minutes. 
3. Once the dough has sufficiently kneaded, transfer to a clean surface. Fold over a few times and then place in a clean mixing bowl. Cover with a damp cloth or plastic wrap, and allow to rise at room temperature for 2 hours, or until doubled in size. 
4. While the dough is rising, prepare the filling. Put the sugars, cinnamon, and salt into a small bowl. Whisk well to combine. Reserve. 
5. Once the dough has sufficiently risen, turn out onto a lightly floured surface and fold over a few times. Roll out to a large rectangle, about 18 x 13 inches. Spread the softened butter over the surface of the dough, leaving a ½-inch border at the top (this helps in sealing the rolls). Sprinkle the filling over the butter.
6. Starting from the long end closest to you, roll the dough up like a jellyroll, ending with the unbuttered edge. Press along the long side to seal. Turn the dough so the seal is on the bottom, and then cut into 12 even pieces. 
7. Line the baking pan with parchment and then place the rolls, cut side down, onto the parchment. Tuck the ends of each roll underneath to prevent them from opening while baking.  Loosely cover with plastic wrap and allow to rise for 30 minutes.
8. Once the rolls have sufficiently risen, heat the oven to 325°F and set the timer to 25 minutes. After the oven preheats for 5 minutes, insert the pan into the lowest rack position. Bake until the buns are cooked through and the tops are golden but not too dark, checking after around 18 minutes of baking time. 
9. While the buns are baking, prepare the glaze. Put the sugar, salt, and honey into a medium mixing bowl. Slowly add the milk while whisking. Continue to whisk until the mixture is smooth. If it seems too thick, thin it with water, 1 teaspoon at a time. The glaze should be thin enough to be transparent after it coats the hot buns. 
10. Once the buns have finished baking, remove from the oven and allow to rest for about 5 minutes. Using a pastry brush, liberally brush the glaze over the tops and sides of each honey bun. Serve warm or at room temperature.