01 - Preheat the oven to 350°F. Line a 9x9-inch baking pan with parchment paper, leaving an overhang for easy removal.
02 - Whisk together all-purpose flour, ground ginger, ground cinnamon, ground cloves, ground nutmeg, baking soda, and salt in a medium bowl.
03 - In a large bowl, whisk melted butter with brown sugar and granulated sugar until combined. Add molasses, egg, and vanilla extract, mixing until smooth.
04 - Gradually fold the dry ingredient mixture into the wet ingredients until just combined, avoiding overmixing.
05 - Evenly spread the dough into the prepared baking pan.
06 - Bake for 20 to 22 minutes until edges are set and the center remains slightly soft. Avoid overbaking.
07 - Allow the bars to cool completely in the pan on a wire rack.
08 - Whisk powdered sugar, milk, and vanilla extract in a small bowl until smooth and pourable. Drizzle over cooled bars.
09 - Cut into 16 squares and serve.