Preheat the oven to 350F and line a 9x13 pan with baking parchment.
In a large bowl, whisk together the flour, baking soda, ginger, cinnamon, nutmeg, salt, and cloves. For a strongly flavored, European-style gingerbread, use the full amount of the ginger and the cloves. For a lighter, milder (but still boldly spiced!) Gingerbread cake omit the cloves and use just 2 tsp of ginger.
In another bowl or large jug, whisk together the oil, brown sugar, molasses, eggs and 3/4 of the orange zest.
Whisk the wet ingredients into the dry until you have a thick batter. Whisk in the boiling water until the mixture is smooth and glossy.
Transfer the batter to the prepared tin. Drop it down on the countertop a few times to knock out any air bubbles, and bake for 30-35 minutes until a wooden skewer or the tip of a sharp knife inserted into the middle of the cake comes out clean.
Once the tin is cool enough to touch remove the cake and leave to cool on a wire rack.
To make the glaze, whisk together the powdered sugar and orange juice until smooth, then stir in the heavy cream and the reserved orange zest. Pour over the cake once it is completely cool.