Sounds like my favourite technique though I tend to prefer a farmer's cheese/potato filling since it's a bit tangier (similar to Cheemo's potato and aged white cheddar pierogi) from a shop near me. Sadly, that variety is not listed on their website and is not in stock all the time so I have to check in person. OTOH, I noticed that JJ Wilk does show them on their website. Sadly a bit of a drive to hit their factory store.
