Before you start, if you want to add the smokiness, purchase a bag of hickory or mesquite chips and follow the instructions. Ours said to soak for 25 minutes in water, drain and place in a aluminium foil tray.
Mix together 1 1/2 cups of gf self raising flour, ½ cup of gf plain flour, 1 cup white sugar, 150g of softened butter, ¾ cup of milk and 3 eggs.
Also stir in the zest of 1 large orange, the juice of 1 orange and approx 1 tbsp of washed fresh thyme.
If you want to just use your oven and leave the smokiness out, bake in a preheated oven at 140oC for approx 1 hour.
However to add in that subtle smokiness to the cake, pour the cake batter into aluminium foil baking trays (I used 2 medium sized rectangular ones). After trial and error I highly recommend placing the trays with the hickory chips on the bbq plate and the trays with the cake batter raised off the bbq on a rack. Ours has a rack attached to the lid so it keeps it far away from the flame. Otherwise you end up with a la charchar. Cook on the lowest bbq temperature.
Smoked Whiskey Frosting
To make the smoked whiskey frosting, place ¼ cup whiskey with 250g of cold butter in an aluminium tray (time to smoke some more!), and place it on the bbq, preferably on the rack, for about 10 minutes (longer if possible).
Place in a mixing bowl with 3 cups of gf pure icing sugar and mix until fluffy.