"Food for me was a connecting link to my grandmother, to my childhood, to my past. And what I found out is that for everybody, food is a connector to their roots, to their past in different ways. It gives you security; it gives you a profile of who you are, where you come from." - Lidia Matticchio Bastianich
My mom-in-law makes this flour at home. It is a pantry staple. So whenever you want to make khatta (sour) dhokla, you directly use the flour. You can also, soak rice & urad daal and make it like you would do for idli. But the main difference is in order to ferment, a generous amount sour yogurt or buttermilk is used and hence the name "Khatta" (Sour) Dhokla.
The use of Khatta Dhokla flour (or loat in Gujarati) is not limited to make just Khatta Dhokla but many more savory dishes. I am hoping to cover them one by one. :-)