In a large skillet, cook the bacon over moderately high heat, stirring, until browned and crisp, about 7 minutes. Drain the bacon, leaving 1 tablespoon of the fat in the pan. Add the leeks and thyme to the skillet, season with salt and white pepper and cook over moderate heat, stirring occasionally, until the leeks are softened but not browned, about 5 minutes. Transfer to a bowl and let cool. Stir in the bacon and cheese.