Preheat the oven to 180°C (160°C fan-forced). Grease a 20cm x 30cm lamington pan. Line base and two long sides with baking paper, extending paper 2cm above edges of pan.
Melt the butter and honey in a small saucepan over a medium heat. Bring to the boil and remove from the heat. Stir in the bicarb soda. Cool for 10 minutes.
Sift the flours and spices into a large bowl. Stir in the brown sugar. Make a well in the centre. Add the butter mixture and stir until combined. Add the egg. Mix until well combined. Press mixture into the prepared pan.
Bake for 20-25 minutes or until golden and firm to touch. Cool slice in pan.
Meanwhile, to make the Icing, place the icing sugar and softened butter in a bowl. Add enough hot water, stirring, to make a smooth, thick icing. Add extra water or icing sugar as needed. Tint icing with pink food colouring.
Spread icing on top of cooled slice and allow to set. Cut slice into bars to serve.
