What is pyshka? It some kind of donut or pikelet. This is piece of bakery dough boiled in oil with sugar powder.
Why is Leningradskaya Pyshka histirical brand of Saint-Petersburg? Because it associate with Soviet Union in the city. I think it was Soviet fast-food))
This kind of food really tasty and cheap. You can find cafe with Pyshki in center of the city. It's popular again.