You can't use protein powder cup for cup as a substitute for flour. Think of it as a "glue" for all the other ingredients.

It contains no gluten, so it will not rise like flour. The texture can be rubbery if too much is used and I find it requires a lot of fat - butter, nut butters, etc. to give it a good texture. It is best used in small amounts and cautiously with other ingredients like soy flour, flaxmeal, gluten flour, etc.

I've used it successfully in cookies and halvah and recently made a cheesecake for Marlaine and Ruth with Creamsicle flavoured Protein Powder.

Karen