In a small bowl, prepare your cinnamon swirl filling by mixing together the brown sugar, cinnamon, ginger, nutmeg, cardamom and flour until well combined. Set aside.
½ (85g) cup brown sugar, ⅓ (40g) cup all-purpose flour, 2½ tsp ground cinnamon, ¼ tsp ground ginger, ⅛ tsp ground nutmeg, ⅛ tsp ground cardamom
Flour your work surface well and turn out the dough gently. Pre-shape by gently stretching it into a loose square about 12x12 inches.
Sprinkle approximately ⅔ of the cinnamon sugar mixture evenly over the surface, leaving about a ½-inch border around the edges.
Perform a letter fold: Fold one long third of the dough toward the center. Fold the opposite third over it, just like folding a letter. Gently press the dough to secure the layers without squeezing out all of the air.
You will now have created a long rectangle shape about 5 inches wide. Sprinkle the remaining ⅓ of the cinnamon sugar mixture over the folded dough, again leaving a small border around the edges. This border is important! Don't skip it.
Starting at one short end, gently roll or fold the dough over itself to create a compact loaf similar to a football shape seam side up.
It's very important to pinch and stich all of the seams together at the ends of the loaf and the seam along the top to make sure none of the cinnamon sugar filling can leak out. Once the bread goes in the refrigerator, any open holes will cause leakage we don't want.
Flour your banneton (the dough can be sticky so don't forget this) and transfer your loaf seam side up into the floured banneton. Cover the banneton with a cover or plastic wrap.
Transfer the dough to the refrigerator overnight for continued cold fermentation (this step can't be skipped).