Make the Tangzhong: Combine the milk and flour in a small saucepan and place over medium heat. Whisk constantly until the mixture becomes thick and paste-like (around 2 minutes). Remove from heat and let cool for 10 minutes.

Make the Dough: Place the Tangzhong in the stand mixer bowl. Add all dough ingredients except the butter. Mix with a spatula to roughly combine ingredients (dough will be shaggy). Place the bowl on the stand mixer fitted with the dough hook attachment and knead on low speed. Continue mixing until the dough passes the windowpane test, approximately 12-15 minutes. With the mixer on low, add softened butter in 3 stages. Continue mixing until the butter is fully incorporated, about 2-3 minutes. Shape into a ball, place in a lightly greased, large bowl, and cover with plastic wrap. Set aside to rise until about doubled in size (around an hour and a half).

Make the Filling: While the dough is rising, place butter in a saucepan over medium heat. Stir often until butter foams, then browns, about 5-7 minutes. Turn off the heat and stir in cocoa powder. Mix in light brown sugar and salt and set aside to cool.

Shape the Rolls: Line a 9” x 13” pan with parchment and butter all sides. On a lightly floured surface, turn out your risen dough and roll into about a 20” x 12” rectangle. Spread the filling over the dough in an even layer, then top with chopped chocolate. Starting on the long edge, tightly roll up the dough into a log. Using a sharp, serrated knife, trim off both ends. Then, using your knife or preferably unflavored dental floss, cut into 12 equal rounds (approx. 1 ½ inch each). Place rolls in prepared pan, cover, and let rise in a warm spot for 45 minutes until puffed up.

Make the Icing: Mix all icing ingredients either by hand or in a stand mixer fitted with the paddle attachment until smooth and fluffy, 2-5 minutes.

Bake & Serve: Preheat oven to 350°F. Bake rolls until they get a slight color on top, 25-30 minutes. Let rolls cool for at least 10 minutes, then spread with icing.