Preheat the oven to 180 degrees C.
Take a bread rectangle tin, butter it and sprinkle with a gluten free flour, for example the millet flour, so the cake won't stick.
Sieve all flours into a large mixing bowl, mix with a baking powder, baking soda and spices (cinnamon, mixed spice and ginger).
Place the bananas, black treacle, sugar, oil and beer in a blender. Blend thoroughly. Pour it into the mixing bowl with flours and the rest of ingredients. Leave for 5-10 minutes so the mix will have time to thicken.
In the end add the raisins and crushed walnuts, mix all again and place all the batter in a prepared rectangular bread baking tin.
Bake for around 45 minutes, but in the end of baking check if a skewer place in the middle of the cake comes out clean. If it is clean, the cake is ready, if it is sticky, add few minutes and check again. You need to do this to avoid drying out the cake.
Leave the cake too cool. Gently turn it up side down on a platter or a board.
Prepare the icing. Mix the icing sugar with a tiny bit of water (or lemon juice) and add a handful of prepared earlier *candied peel. Pour the icing on top of the cake and watch it pour down the sides.
Enjoy!