Ingredients
4 boneless, skinless chicken breasts (about 2 pounds total)
4 tablespoons unsalted butter, divided
4 cloves garlic, minced (or 1 teaspoon garlic powder)
2 medium lemons, thinly sliced (plus 1 tablespoon lemon juice, optional)
1 1/2 teaspoons salt
1/2 teaspoon black pepper
Heavy-duty aluminum foil for wrapping packets
Directions
Prepare the foil: Tear off 4 large sheets of heavy-duty aluminum foil, each about 12–14 inches long. Lightly crimp up the edges a bit so the juices will stay inside when you fold them into packets.
Season the chicken: Pat the chicken breasts dry with paper towels. Sprinkle both sides of each breast evenly with the salt and black pepper. If using garlic powder instead of fresh garlic, sprinkle it over the chicken now as well.
Build the packets: Place one seasoned chicken breast in the center of each foil sheet. Top each piece of chicken with 1 tablespoon of butter (you can cut it into a few small pieces so it melts evenly). If using fresh minced garlic, divide it evenly over the tops of the chicken breasts. Lay 2–3 lemon slices over each chicken breast, and if you like a little extra brightness, drizzle about 1 teaspoon lemon juice over each one.
Seal the packets: Bring the long sides of each foil sheet up and together over the chicken and fold them down tightly, then fold in the short ends to seal completely. You want each packet well sealed so the steam and juices stay inside and the slow cooker stays clean.
Arrange in the slow cooker: Place the foil packets seam-side up in the bowl of your slow cooker. It’s fine if they overlap slightly or lean against each other, as long as each one is sealed. Cover the slow cooker with the lid.
Cook: Cook on LOW for 3 1/2 to 4 1/2 hours, or until the chicken is cooked through and reaches an internal temperature of 165°F. The exact time will depend on the thickness of your chicken breasts and your slow cooker model. Avoid lifting the lid too often so you keep the heat and moisture in.
Rest and open carefully: Turn off the slow cooker and let the packets rest for about 5 minutes. Using tongs, carefully transfer each foil packet to a plate or baking sheet. Open each packet slowly and away from your face, as the trapped steam will be very hot.
Serve: Spoon some of the buttery lemon garlic juices from each packet over the chicken before serving. Garnish with the cooked lemon slices (and fresh lemon slices, if you like). Serve the chicken directly in the open packets for a fun, no-mess presentation, or transfer to plates and pour the juices over the top.