Step 1: Thoroughly wash the dandelion greens, trim tough ends, and roughly chop into 1-2 inch pieces. If desired, blanch greens for 2-3 minutes in boiling salted water, then shock in ice water to reduce bitterness; drain well.
Step 2: In a large skillet or Dutch oven, cook the chopped bacon over medium heat until crispy. Remove bacon bits with a slotted spoon and set aside, reserving 1-2 tablespoons of rendered fat in the skillet.
Step 3: Add minced garlic to the skillet with the reserved bacon fat (add olive oil if more fat is needed). Sauté over medium-low heat for 30-60 seconds until fragrant, being careful not to burn it.
Step 4: Add the chopped dandelion greens to the skillet. Stir well to coat with bacon fat and garlic. Cook for 5-10 minutes, stirring occasionally, until the greens are tender and wilted.
Step 5: Remove the skillet from heat. Stir in the apple cider vinegar or lemon juice and red pepper flakes (if using).
Step 6: Taste and season with salt and freshly ground black pepper as needed. Remember the bacon adds salt, so season carefully. Serve warm, garnished with the reserved crispy bacon bits.