1. Preheat the oven to 375°F (190°C).
2. In a large mixing bowl, combine flour, granulated sugar, baking powder, and salt.
3. In another bowl, whisk together the milk, melted butter, and egg.
4. Pour the wet ingredients into the dry ingredients and mix until a dough forms.
5. On a floured surface, roll out the dough into a rectangle about 1/4 inch thick.
6. Spread the softened butter over the dough evenly.
7. In a small bowl, mix brown sugar and cinnamon together and sprinkle it over the buttered dough.
8. Roll the dough tightly from one end to the other and cut into 12 equal pieces.
9. Place the rolls in a greased baking dish and bake for 15-20 minutes or until golden brown.
10. While rolls are baking, make the icing by mixing powdered sugar and milk until smooth.
11. Drizzle icing over warm cinnamon rolls before serving.