Bring water to a boil, add frozen pierogi. Simmer 5 minutes and remove.
You can enjoy right after you take them out of the pot with melted butter. Or add some zest by sautéing cooked pierogi in butter over medium heat until golden, 2 -3 minutes per side. Remove and drizzle with spicy brown mustard. Our favorite is Bacik's Musztarda Kozacka (Polish mustard).