For the filling: In a small bowl, combine the light brown sugar and cinnamon; set aside.
For the dough: Adjust the oven rack to the middle position. Line a 9x9-inch square or round baking dish with parchment paper; set aside.
In a liquid measuring cup, add ¼ cup milk and microwave until it reaches 110°F (about 15–20 seconds). Stir in the yeast and 1 teaspoon sugar and let rest until the mixture becomes bubbly, about 5 minutes.
In a large bowl, whisk together the flour, baking powder, and the remaining 3 tablespoons plus 2 teaspoons sugar.
Stir in 3 tablespoons of cooled, melted butter, yeast mixture, salt, vanilla, and the remaining 1 cup of warm milk (110°F) until the dough forms; it will be sticky. Transfer the dough to a well-floured counter and knead until a smooth ball forms, about 2 minutes.
Roll the dough into a 12×9-inch rectangle. Spread 2 tablespoons of softened butter evenly over the dough, leaving a ½-inch border on the far edge.
Sprinkle the brown sugar and cinnamon mixture evenly over the butter and lightly press it into the dough. Using a bench scraper, loosen the dough from the counter.
Starting with the edge closest to you, roll the dough tightly into a log and lightly pinch the seam to seal.
Roll the dough seam-side down and cut the log into 9 equal pieces. Stand the rolls on end and gently reform the ends that were pinched during cutting. Arrange cut-side up in the prepared baking pan.
Brush the tops with the remaining 2 tablespoons of butter. Cover loosely with plastic wrap and let the cinnamon buns rise in a warm place for 30 minutes, or until doubled in size.
To assemble: Preheat the oven to 350°F (175°C). Bake the cinnamon rolls for 23–25 minutes, or until deep golden brown and the filling is melted. When the buns are done, loosen the edges with a paring knife and let cool for 5 minutes.
Using a potholder, invert a large plate over the pan and flip the pan upside down; remove the pan and parchment paper. Then reinvert the cinnamon rolls onto a wire rack set inside a parchment-lined baking sheet and let cool for another 5 minutes.
For the icing: Place the cream cheese, butter, vanilla, powdered milk, and a small pinch of kosher salt in the bowl of a stand mixer fitted with the paddle attachment.
Beat until smooth and well combined. Add the powdered sugar and dry whole milk (if using) and beat until smooth. Pour the icing evenly over the cinnamon rolls and spread with an offset spatula. Serve.
Camila’s Tip: Roll the dough to an even thickness from end to end to prevent uneven cinnamon rolls. Lightly dust the work surface or rolling pin if the dough sticks.