Mama's Kitchen Nightmare

So, imagine my dadiji's famous sarson ka saag recipe gets copied by a popular restaurant chain in our city. They use the exact same recipe, same portion size, even same packaging. The twist: they charge way more than dadiji does.

Now, what do we do? The restaurant owners say it's their own recipe, they got it from some other chef. But dadiji is sure she saw one of their chefs trying to get her recipe book from our kitchen.

Do they have a case against my papa (the restaurant owner)? Or is it all a big misunderstanding? In tort law, what remedy applies here? Is it an action for passing off or maybe some other tort?