20 frozen potato-cheese pierogies (about 28 oz; not thawed)
3 tablespoons olive oil
6 bacon slices (6 oz), chopped
1 large onion, halved lengthwise, then thinly sliced crosswise
4 garlic cloves, chopped
1 1/2 lb Savoy cabbage, halved, cored, and thinly sliced (8 cups)
1/2 cup water
1/4 teaspoon salt
1/3 cup chopped fresh dill

Accompaniment: sour cream

Parboil pierogies in a 6- to 8-quart pot of boiling salted water, uncovered, stirring occasionally, 1 minute less than package instructions indicate (pierogies will not be completely cooked). Transfer with a slotted spoon to a colander to drain. Pat dry.

Heat 1 tablespoon oil in a 12-inch heavy skillet over moderately high heat until hot but not smoking, then saut half of pierogies, turning over once, until golden, about 4 minutes per batch. Transfer to a large platter and keep warm, loosely covered with foil. Add 1 tablespoon oil to skillet and saut remaining pierogies in same manner, transferring to platter.

Cook bacon in same skillet over moderately high heat, stirring occasionally, until crisp and golden, 6 to 8 minutes, then transfer to paper towels to drain.

Pour off all but 1 tablespoon fat from skillet, then add remaining tablespoon oil and saut onion over moderately high heat, stirring, until golden, about 8 minutes. Reduce heat to moderate, then stir in garlic, cabbage, water, and salt and cook, covered, stirring occasionally, until cabbage is tender, 5 to 7 minutes. Transfer to platter with pierogies and sprinkle with bacon and dill.