First, gently heat the milk in a small saucepan over medium heat until it is steaming and small bubbles form around the edges (this is called scalding). Do not let it boil. Remove from the heat and let it cool until it is lukewarm, about 90-100°F. If it's too hot, it will kill the yeast. Pour the lukewarm milk into the bowl of a stand mixer (or a large mixing bowl). Stir in the honey, then sprinkle the active dry yeast over the top. Let it sit for 5-10 minutes until the yeast becomes foamy and bubbly. This "blooming" process confirms your yeast is active.
To the yeast mixture, add 3 tablespoons of the melted butter, the room-temperature egg, and the salt. Whisk briefly to combine. Fit your stand mixer with the dough hook attachment. Add about half of the flour to the bowl and mix on low speed until it is just combined. Gradually add the remaining flour and continue to mix until a shaggy dough forms.
Increase the mixer speed to medium-low and knead the dough for 8-10 minutes. The dough is ready when it is smooth, elastic, and pulls away from the sides of the bowl. To test for doneness, you can do the "windowpane test": tear off a small piece of dough and gently stretch it between your fingers. If you can stretch it thin enough to see light through it without it tearing, the gluten is well-developed. If kneading by hand, turn the dough out onto a lightly floured surface and knead for 10-12 minutes.
Lightly grease a large, clean bowl with cooking spray or oil. Form the kneaded dough into a ball and place it in the bowl, turning it over once to coat the top with oil. Cover the bowl tightly with plastic wrap or a damp kitchen towel. Let the dough rise in a warm, draft-free spot for 60-90 minutes, or until it has doubled in size.
Gently punch down the risen dough to release the air. Transfer it to a lightly floured work surface. Roll the dough out into a rectangle that is approximately 12x15 inches and about ½ inch thick. Fold the rectangle in half lengthwise. Using a pizza cutter or a bench scraper, cut the folded dough into 24 even squares (a 4x6 grid).
Line two baking sheets with parchment paper. Arrange the dough squares on the prepared baking sheets, leaving a little space between them. Cover the sheets loosely with plastic wrap and let the rolls rise for another 30-45 minutes, until they look puffy. While the rolls are rising, preheat your oven to 350°F (175°C). Once risen, bake the rolls for 12-15 minutes, or until the tops are lightly golden brown.
While the rolls are baking, prepare the butter. In a medium bowl, use an electric mixer to beat the softened butter until it is light and creamy. Add the powdered sugar, honey, cinnamon, and a pinch of salt. Beat again until everything is well combined and fluffy.
As soon as the rolls come out of the oven, brush the tops with the remaining 1 tablespoon of melted butter. This gives them a beautiful shine and extra flavor. Serve the rolls warm with a generous amount of the homemade honey cinnamon butter.