Add the all-purpose flour, caster sugar, and egg to a mixing bowl. Whisk until roughly combined.

Stir the instant yeast into the warm milk. Let it stand for about 5 minutes until dissolved.

Gradually add the yeast mixture to the flour mixture. Mix until a shaggy dough forms.

Turn the dough onto a clean work surface. Knead it for 5 minutes until it begins to smooth out.

Add 45 g of the unsalted butter one small cube at a time. Knead after each addition until all butter is fully absorbed and the dough is smooth and elastic.

Lightly grease a clean mixing bowl with a little butter. Place the dough inside and cover it.

Proof the covered dough in a warm place for 90 minutes. Continue proofing until it has doubled in size.

Press the risen dough down to release trapped air. Roll it into an even rectangle about 12 x 9 inches.

Mix the remaining 50 g unsalted butter, brown sugar, and ground cinnamon in a bowl. Spread the cinnamon filling evenly over the dough rectangle.

Roll the filled dough tightly from the long side into a log. Cut the log into 9 equal rolls, about 1 inch thick.

Arrange the rolls cut-side up in the 8 x 8 inch square baking pan. Cover the pan.

Proof the covered rolls for 60 minutes in a warm place. Let them rise until doubled in size and puffy.

Preheat the oven to 190°C (375°F). Bake the rolls for 12 to 15 minutes until golden brown.

Transfer the pan to a wire rack and cool the rolls for 10 minutes. Spread the cream cheese frosting over the warm rolls before serving.