- Preheat the oven to 350 °F (180 °C) and grease a 9-x-13-inch cake pan.
- Beat the butter and brown sugar until light and fluffy. Beat in the molasses, then add the eggs one at a time, beating well after each addition. Stir in the lemon juice, and ginger.
- In a separate bowl, sift the flour with the spices and the salt. Add this to the butter mixture and stir until blended. Stir the boiling water and baking soda and add this quickly to the batter, stirring quickly and then stir in the crystallized ginger (the batter will be fluid). Scrape the batter into the prepared pan and bake for 45 minutes, until a tester inserted in the centre comes out clean. Cool the cake completely in the pan and cut into squares to serve with a dusting of icing sugar and a dollop of whipped cream.
The cake will keep, wrapped, for up to 3 days.