Gingerbread Cookie Bars

Name: Gingerbread Cookie Bars
Prep time: 20 min
Cook time: 22 min
Total time: 42 min
Cuisine: American
Ingredients: ¾ cup unsalted butter (melted); 1 cup dark brown sugar (firmly packed); 1 large egg (room temperature); ¼ cup unsulphured molasses (it should say unsulphered on the label, I used "Grandma's" brand ); 1 teaspoon vanilla extract; 2 cups + 2 Tablespoons all-purpose flour; 1 teaspoon cornstarch; ¼ teaspoon baking powder; ¼ teaspoon baking soda; ½ teaspoon salt; 2 teaspoon ground ginger; 1 ½ teaspoon ground cinnamon; ½ teaspoon ground cloves; ¼ teaspoon nutmeg; 6 Tablespoons salted butter softened; 6 oz cream cheese (softened); ½ tsp pure vanilla extract; 2 ¼ cups powdered sugar; 2 tsp cornstarch**; Sprinkles for decorating (optional)