Preheat oven to 350 degrees F. Grease a 9 x 13-inch pan with cooking spray.
Cream the sugar and butter until light and fluffy in a large bowl or stand mixer. Beat in the egg and vanilla, and then stir in the molasses.
Sift the flour, unsweetened cocoa powder, baking soda, cinnamon, ginger, cloves, salt, and pepper in another bowl. Fold the dry ingredients into the molasses mixture. Slowly pour in the hot water and mix until smooth. The batter will be thin.
Bake for 20-35 minutes or until a toothpick inserted in the middle comes out clean. Serve warm topped with sweetened whipped cream, the Vanilla Cream Sauce, or simply dusted with powdered sugar.
Vanilla Cream Sauce
Add sugar, butter, and cream to a medium saucepan and cook over medium heat, stirring occasionally, until the butter has melted.
Bring to a boil, stirring frequently, for 3-5 inuites. Remove from the heat, stir in vanilla, and let cool slightly before serving over the gingerbread cake.
Notes
Vanilla Cream Sauce: The sauce can be made ahead and stored in an airtight container in the refrigerator for up to 3 days.
Storing: This cake keeps well at room temperature for up to 2 days, but can also be stored wrapped well in the refrigerator for up to 1 week.
Serving: Let the cake cool slightly before cutting into squares and serving.