Allergy Free Baking Powder (Nourishing Traditions)
This has the same ingredients as what is sold at health food shops, but I'm sure it would be much cheaper to make at home.
1 part potassium bicarbonate (baking soda)
2 parts cream of tartar
2 parts arrowroot
Use 2 level teaspoons per cup of flour, which is the same as commercial baking powder or the EDC recipe.
After consulting with my allergy go-to girl Jo (love your work), I tried this and it works beautifully. So I sent some home with both grandmothers and my sister so that all their baking is now allergy friendly too.
I should be an expert at converting Self-Raising Flour recipes back to flour and baking powder soon!