Warm the milk and mix with yeast and 1 teaspoon of sugar. Let sit for 5–10 minutes until foamy.
In a bowl, mix yeast mixture, remaining sugar, egg, egg yolk, and melted butter.
Add flour and salt and mix until a soft dough forms.
Knead dough for 8–10 minutes until smooth and elastic.
Place dough in a greased bowl, cover, and let rise for 1 hour or until doubled in size.
Roll dough into a rectangle. Spread softened butter evenly over the surface.
Mix brown sugar and cinnamon and sprinkle evenly over the buttered dough.
Roll tightly from the long side and cut into 9–12 rolls.
Place rolls in a greased baking dish, cover, and let rise for 30–45 minutes.
Bake at 350°F (175°C) for 22–25 minutes until lightly golden.
Beat icing ingredients until smooth and spread over warm rolls.
