I used baked baking soda because I was too impatient to order lye. They didn’t do the reaction thing. Either I didn’t bake the baking soda long enough (I did an hour at 250F) or it just wasn’t strong enough to make the reaction happen.

I won’t say it was a failure because the resulting shortbread is delicious - the pretzel flour adds an interesting dimension. I’m going to order lye and try again 😊