Step 1: Reduce the apple cider. In a small saucepan over medium heat, simmer the 2 cups of apple cider until it has reduced to exactly 1/2 cup. This should take about 15-20 minutes. Set aside to cool completely.
Step 2: Preheat your oven to 350°F (175°C). Grease an 8×8 inch square baking pan and line it with parchment paper, leaving an overhang on two sides for easy removal.
Step 3: In a large mixing bowl, whisk together the melted butter, dark brown sugar, and granulated sugar until well combined.
Step 4: Add the egg, molasses, vanilla extract, and the cooled apple cider reduction. Whisk vigorously until the batter is smooth and slightly glossy.
Step 5: In a separate medium bowl, sift together the flour, ground ginger, cinnamon, cloves, nutmeg, baking powder, and salt.
Step 6: Gently fold the dry ingredients into the wet mixture using a spatula. Mix until just combined; do not over-mix to ensure the apple cider and gingerbread blondies stay chewy.
Step 7: Pour the batter into the prepared baking pan and spread it evenly into the corners.
Step 8: Bake for 22-25 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out with just a few moist crumbs.
Step 9: Remove from the oven and allow the apple cider and gingerbread blondies to cool completely in the pan before lifting them out and slicing into 16 squares.