To a stand mixer fitted with a dough hook add the milk, sugar and yeast. Stir and let sit for 10 minutes until foamy.
Next add in the eggs and 2 1/2 cups of flour. Starting the mixer on low, gently knead the dough together, bumping up the speed to 2 and then 4. Once it comes together add in the softened butter. Knead the mixture on speed 4, or medium, for about 5-8 minutes or until it begins to make a slapping sound in the bowl and looks smooth. If it sticks to your fingers add a little more flour.
Remove from bowl and gently knead on a lightly floured surface, about 10 times. Roll into a ball and place it in a well oiled bowl. Cover with plastic wrap and a clean kitchen towel then place in a warm area for about 1 1/2 to 2 hours or until it doubles in size.
Grease a 10-inch cast iron skillet. Set aside. In a small bowl combine the brown sugar, cinnamon and cornstarch.
Remove the risen dough from the bowl and gently roll out on a floured surface with a rolling pin. Roll into a rectangle roughly 12x18. Spread the 3 tbsp. softened butter over the dough and sprinkle with the filling mixture. Roll the dough on top of itself starting at the long end and rolling up. Cut into 10 even rolls.
Place into the prepared skillet. Cover with plastic wrap and a towel then place in a warm area until puffy and slightly risen, about 30 minutes. Or, cover with plastic wrap and refrigerate overnight. The next morning let the rolls come to room temperature, about 45 minutes, before baking.
Preheat oven to 375°F and place an oven rack in the middle.
Bake the rolls for 20-25 minutes or until puffed, golden brown and cooked through.
Remove from oven and let cool slightly. To make the frosting, add the powdered sugar, butter and milk to a small bowl and whisk until smooth and creamy. Once the rolls have cooled, liberally spread with the frosting. Will keep covered, at room temperature for 3-4 days.
Recipe Courtesy of Megan Mitchell