2 pounds leeks, white and tender green parts only, sliced crosswise 3/4 inch
Kosher salt and freshly ground pepper
Heat a large skillet. Add the bacon and cook over moderate heat until crisp around the edges, about 6 minutes. Transfer the bacon to a paper towel–lined plate and wipe out the skillet.
Melt the butter in the skillet over high heat until starting to brown. Reduce the heat to moderate, add the leeks and cook, stirring, until tender, 6 to 8 minutes. Return the bacon to the skillet and toss. Season with salt and pepper and serve.