Boil the pierogies: Bring a large pot of salted water to a rolling boil. Gently drop in the frozen pierogies, being careful not to overcrowd the pot. Stir occasionally to prevent sticking. Boil for 5–6 minutes, or until the pierogies float to the surface — that’s the sign they’re perfectly cooked. Remove them with a slotted spoon and set aside on a plate.

Prepare the onion butter: In a large skillet, melt the butter with olive oil over medium heat. Add the sliced onions and cook slowly, stirring often, until they turn golden brown and fragrant — about 10–12 minutes. This step adds a rich, savory flavor that pairs beautifully with the pierogies.

Pan-fry the pierogies: Once the onions are caramelized, push them to the side of the skillet. Add the boiled pierogies in a single layer. Fry for 3–5 minutes per side, or until golden and lightly crispy. If the pan looks dry, add a little more butter or olive oil.

Season and serve: Season the pierogies lightly with salt and pepper, then toss them with the caramelized onions so they’re fully coated in buttery goodness. Transfer to a serving plate and top with a dollop of sour cream. Sprinkle green onions or bacon bits on top for an extra indulgent touch.

Optional oven method: If you prefer baking, preheat your oven to 400°F (200°C). Arrange frozen pierogies on a parchment-lined baking sheet, brush lightly with oil or melted butter, and bake for 18–20 minutes, flipping halfway through. They’ll come out crispy and golden.