Inga’s Kitchen

Great Aunt Inga is a fantastic bread baker. She had been living with us for the last few months but recently, and unexpectedly packed up and returned to Russia, leavings us melancholy and bread-less. We have decided to pick up where she left off but seem to be missing a key ingredient and the resulting breads have proven to be, well, disappointing. We located her (well-loved) recipe but unsurprisingly, it’s written in code. Aunt Inga was always a bit suspicious of people and often thought that someone was watching her. Ridiculous, I know! Anyway, it seems that we have been able to find all of the ingredients but one. Can you help uncover the missing ingredient so that we can make the morning bread?

What is the missing ingredient? (Solvers get a secret surprise. Check within.)