Preheat the oven to 350 degrees F. Grease or line a 13x9 inch baking pan with parchment paper.
In a large mixing bowl whisk together the flour, ginger, cinnamon, nutmeg, cloves, baking powder, and salt. Set aside.
In a large mixing bowl with an electric mixer or stand mixer with a paddle attachment, cream together the butter and sugars until light and fluffy. Add molasses, egg, and vanilla.
Add dry ingredients to the wet mixture and stir to combine. Slowly pour in the hot water and stir until smooth (batter will be thin).
Pour the batter onto the prepared baking sheet and bake for 25-30 minutes or until a toothpick inserted in the center comes out clean.
In the meantime, prepare the frosting. In a large bowl, cream together the cream cheese and butter until fluffy and no lumps remain. Turn the mixer on low and beat in 2 1/2 cups of powdered sugar, vanilla and cinnamon until combined and desired consistency is reached. . If the frosting is too thick, add milk, if it's too thin, add more powdered sugar.
Swirl frosting onto cooled cake and add gingerbread cookies and sprinkles. Cut into squares and enjoy!