Prepare the Dough: In a large mixing bowl, combine the softened butter and cream cheese. Beat until smooth and creamy. Gradually add the flour, mixing until a soft dough forms. Cover the dough with plastic wrap and refrigerate for a minimum of 1 hour to allow it to firm up.

Make the Filling: In a medium bowl, mix the brown sugar, white sugar, cinnamon, and ground hazelnuts. Set aside.

Roll Out the Dough: Preheat the oven to 180°C (350°F). Place the chilled dough on a surface dusted with flour, then split it into two equal parts. Roll each piece into a rectangle, aiming for a thickness of about 1/4 inch.

Assemble the Rolls: Evenly sprinkle the cinnamon-hazelnut mixture over the rolled-out dough. Starting from the longer edge, tightly roll up the dough to form a log. Repeat with the second portion.

Cut and Bake: Slice each log into 1-inch pieces and place the rolls on a lined baking sheet, cut-side down. Place in the oven and bake for 18 to 22 minutes, or until the edges turn a golden brown.

Cool and Serve: Allow the swirls to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely. Enjoy warm or at room temperature!