Make filling: Add 75 g unsalted butter, 50 g brown sugar, 2 teaspoons ground cinnamon, and pinch fine sea salt to a small mixing bowl and mix to form a smooth paste.
Fill: After the first rise, roll the dough out to a rectangle about 12" x 18" (30.5 x 40.5 cm). Dollop the filling on, then spread it out evenly with the back of a spoon.
Roll: Roll the rectangle up from the long side to make 12 standard cinnamon rolls baked in a rectangular pan, or from the short side to make 8 jumbo cinnamon rolls baked in a large round cake pan.
Proof: Arrange the rolls in a lightly greased pan, and cover with plastic wrap or a damp kitchen towel, and leave at room temperature until almost doubled. Towards the end of proofing, preheat the oven to 350˚F (175˚C).
Bake: Bake until golden brown and puffed, about 25–30 minutes. Leave to cool in the pan completely.
Make cream cheese frosting: Add 85 g cream cheese, 40 g unsalted butter, 120 g powdered sugar, and ½ teaspoon vanilla extract to a medium mixing bowl or the bowl of a stand mixer. Start mixing on low speed to incorporate the powdered sugar, then bring it up to medium high and beat until light and fluffy. Slather the frosting on top of the cinnamon rolls after they have cooled completely.
