Preheat the oven to 160 degrees C and grease and flour a square 23cm cake tin.
In a mixing bowl sift together the flour, baking powder, bicarb soda, ginger, cinnamon, nutmeg, cloves and salt.
In the bowl of an electric mixer beat the butter until creamy, then gradually add the sugar and beat until light, about 2 minutes.
Beat in the egg and yolk, then beat in the sour cream, vanilla, ginger and molasses. Add the flour mixture and beat until just blended. Add the hot water and beat until smooth, then pour the batter into the cake tin.