Preheat the oven to 350℉. Spray an 8x8-inch pan with nonstick spray.
In a large bowl, whisk together the brown sugar, butter and molasses. Then whisk in the eggs; whisk until the mixture is light and foamy. Then whisk in the vanilla.
Sift the flour and remaining ingredients (through cloves) into the egg mixture; stir to combine.
Scrape the batter into the prepared pan. Bake for 20 to 25 minutes, just until set. Let cool. Then cut into 9 equal squares and dust with powdered sugar, if using.