Add yeast and lukewarm milk to a large mixing bowl or the bowl of a stand mixer fitted with the dough hook attachment. Stir to dissolve the yeast and allow mixture to sit for about 10–15 minutes while the yeast activates.

Once yeast mixture becomes foamy, add sugar, butter, salt, eggs and flour and mix until a dough ball forms. Knead the dough on low to medium speed for 4 minutes or by hand for 6–8 minutes until smooth. Add only as much flour as needed to prevent sticking.

Transfer dough to bowl lightly coated with cooking spray, cover with plastic wrap then allow dough to rise in a warm place for about 1 hour or until doubled in size.

Roll dough out on a lightly floured surface into a 16" x 21" rectangle with the widest side facing you. The dough will be about ¼" thick. Spray a 9" x 13" baking dish with cooking spray or line with parchment paper and set aside.

In a small bowl, combine the brown sugar, granulated sugar, cinnamon and flour together until combined. Spread soft butter evenly over the surface of the dough, coating all the way to the edges. Sprinkle cinnamon sugar evenly over the surface. Press lightly to adhere the cinnamon sugar and butter together.

Roll the dough along the widest side into a cylinder. Cut the cylinder into 12 equal slices, about 1½"—1¾" thick. Transfer rolls into prepared baking dish, spaced evenly apart, and cover with a kitchen towel. Allow rolls to rise for 1 hour or until the rolls have doubled in size. Preheat oven to 350 degrees.

Bake rolls for 20–22 minutes or until light golden brown on top and centers are firm when pressed. Remove from oven then allow to cool on a rack for 15 minutes while you prepare icing.

Add all ingredients for icing to a medium mixing bowl and beat until fluffy. If icing is a bit thick, just add a tiny bit more milk. If the icing is thin, add a bit more powdered sugar. When the rolls have cooled slightly, spread with icing and serve.