Preheat oven to 350°F (175°C) and line a 9x13 inch baking pan with parchment paper, leaving an overhang on the sides. Grease the parchment paper lightly.

In a medium saucepan or microwave-safe bowl, melt the unsalted butter and unsweetened chocolate together over low heat, stirring until smooth. Remove from heat and let cool slightly.

In a large bowl, whisk together the granulated sugar and light brown sugar into the cooled chocolate mixture until combined. Beat in the eggs one at a time, then stir in the vanilla extract and molasses until well incorporated.

In a separate medium bowl, whisk together the all-purpose flour, unsweetened cocoa powder, ground ginger, ground cinnamon, ground cloves, and salt. Ensure all ingredients are evenly distributed.

Gradually add the dry ingredient mixture to the wet ingredients, folding gently with a spatula until just combined and no streaks of flour remain. Be careful not to overmix the batter.

Pour the brownie batter into the prepared baking pan and spread evenly. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out with moist crumbs attached.

Let the brownies cool completely in the pan on a wire rack before lifting them out using the parchment paper overhang. Once fully cooled, cut into squares and serve.