Preheat oven to 350°F (175°C). Line a 9×9-inch pan with parchment paper.
Whisk together the flour, ginger, baking soda, cinnamon, cloves, and salt.
Cream the butter and brown sugar for 2 minutes until fluffy.
Add molasses, vanilla, and egg; mix until combined.
Add the dry ingredients and mix on low until just combined.
Pour in the boiling water and mix until smooth.
Transfer batter to the pan.
Bake for 30–40 minutes, or until a toothpick comes out clean.
Cool for 30 minutes before slicing.
Serve plain or topped as desired.