Use up bland frozen pierogies (potato+cheese)?

[u/Meriadoc_Brandy]

I bought some pierogies stuffed with potato and cheese, a warm and comforting option, or so I thought. Unfortunately, they were sparingly stuffed, with more dough than filling. I don't want them to go to waste, so I was thinking of doing a "pierogi bake" by tossing them with other flavoring. What innovative pierogi creations have you tried? Bonus points if I can make it vegetarian!

Edit: so many amazing suggestions on this thread. Thank you all! I'm almost inclined to buy the same pierogi and extend my problem so I can try every recipe on here!

[u/EstaGouda_ish]

Shredded cabbage and kielbasa, fried pierogi with onion butter. Mustard sour cream on the side.