You can alter the recipe, make give it a trial run first, as the more subs you make to any recipe the greater the result will be altered (not taste/look the same, different texture or even taste)
There are gluten-free flours available at most major supermarkets these days - they are usually in the health food isle, with the organic grains etc.
You can also make your own flour substitute :
Ingredients
2 cups white rice flour
2/3 cup potato starch*
1/3 cup tapioca starch
Directions
Mix ingredients together. Store in a cool, dry place until ready for baking.
* Important: potato starch is not the same as potato flour.
Use this as a 1:1 substitute for flour (so 1 cup = 1 cup)
WRT ICING SUGAR - PURE Icing sugar is gluten free - Soft Icing Sugar Mix or Icing Mixture contains CORNFLOUR which CAN contain gluten if it is made from wheat.
So play it safe and make sure you are using PURE ICING SUGAR and not any soft or mixed icing sugars.
WRT Custard powder - can contain wheat flour or wheaten cornflour. Have a look at the ingredients to be sure. White Wings used to be Gluten Free, so again, check the box.
Also have a look here: Gluten Free and Easy if you need any other info, great site and very clear to understand.
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