How to Make It
In a large, deep skillet, heat the olive oil. Add the bacon and cook over moderately high heat until crisp, turning once, about 6 minutes. Drain the bacon on paper towels, leaving the fat in the skillet. Coarsely chop the bacon.
Add the mushrooms to the skillet, season with salt and pepper and cook over moderately high heat, stirring occasionally, until lightly browned, about 10 minutes. Stir in the onion and garlic and cook, stirring occasionally, until the onions are softened and lightly browned, about 6 minutes. Add the kale, season with salt and pepper and toss to wilt slightly. Stir in the vinegar, cover and cook over high heat until tender, about 5 minutes. Stir in the bacon and serve right away.