These are not the canape-sized blini, but larger pancakes that are filled with a simple but hearty beef and onion mixture. The flavor comes from the generous amount of onion and frying the mix well, at least 10 minutes.
Use any beef you prefer, including pre-boiled beef from the store.
Instead of chopping the beef you can run it through a meat grinder.
You can also pan fry the rolled blini at the end in a bit of oil for even more flavor.