• To the bowl of a stand mixer fitted with the dough hook attachment, add the flour, granulated sugar, salt, and instant yeast. Mix on low speed for a few seconds to combine.
• In a small bowl, combine the warm water, warm buttermilk, and melted butter. Stir to combine. The mixture should be about 105°F to activate the yeast in the next step.
• With the mixer on low speed, slowly pour the warm liquid mixture into the dry ingredients. Stop to scrape the sides of the bowl as needed.
• Once combined, add the egg and increase the mixer speed to medium. Knead the dough in the mixer for 4-5 minutes, or until the dough is smooth, elastic, and no longer sticky. (If the dough looks too dry, add a tablespoon of water; if it looks too wet, add a tablespoon of flour.)
• Form the dough into a ball and leave it in the mixer bowl. Cover the bowl with a clean kitchen towel and let the dough rest for 5 minutes.
• Preheat oven to 200°F. Lightly spray a 9x9-inch baking dish with nonstick cooking spray and set aside.
• After the dough has rested, transfer it to a lightly floured surface. Roll the dough into a 10x15-inch rectangle, about ¼-inch thick.

Filling

• In a small bowl, combine the melted butter, light brown sugar, cinnamon, and salt. Spread the filling evenly over the entire surface of the dough.

Assembly

• Starting on one of the long edges, roll the dough tightly into a log. Using a sharp knife, cut the log into 9 evenly sized rolls. Place the rolls into the prepared baking dish with the cut sides facing up. Cover the dish with plastic wrap.
• Turn off the warmed oven and place the covered baking dish inside. Let the rolls rise for 40 minutes, or until they have doubled in size. Remove the baking dish from the oven and discard the plastic.
• Drizzle the heavy cream evenly over the tops of the rolls.
• Preheat the oven to 375°F.
• Once preheated, bake the rolls for 15–20 minutes, or until the tops are golden brown.

Cream Cheese Frosting

• While the rolls are baking, make the frosting. In the bowl of a stand mixer fitted with the paddle attachment, combine the softened cream cheese, softened butter, confectioners' sugar, vanilla extract, and kosher salt. Mix on low speed until just combined. Then, increase the speed to high and beat for 4–5 minutes, until the frosting is light and fluffy.
• Once the rolls are baked, remove them from the oven and let them cool slightly.
• While the rolls are still warm, generously spread the frosting over the tops. Serve warm.