Make the Dough: In a large bowl (or stand mixer), combine warm milk, instant yeast, sugar, egg yolks, melted butter, bread flour, and salt. Knead for 6–8 minutes in a mixer or 8–10 minutes by hand, until the dough is smooth and slightly tacky (but not sticky).
First Rise: Place the dough in a lightly oiled bowl, cover, and let it rise for 60–90 minutes until doubled in size.
Make the Filling: Mix the softened butter, brown sugar, and cinnamon together into a paste.
Roll and Fill: Roll dough out into a 14×18-inch rectangle. Spread the cinnamon filling evenly all over. Roll it up tightly from the long edge and slice into 12 rolls.
Second Rise: Place the rolls in a greased 9×13 pan, cover, and let rise again for 45–60 minutes until puffy and nearly touching.
Bake: Bake at 350°F for 20–25 minutes until golden brown and set in the center.
Frost and Serve: Mix the frosting ingredients until smooth. Spread generously over the warm rolls and enjoy!