Prep the pot: Lightly spray the inside of your slow cooker or Instant Pot insert. This helps prevent sticking and makes cleanup easier.
Add the chicken: Place the chicken breasts or thighs in a single layer. If using frozen chicken, separate the pieces so they cook evenly.
Season well: Sprinkle the Italian seasoning, onion powder, salt, and pepper over the chicken.
Add the minced garlic on top.
Add liquids and flavor: Pour in the chicken broth and lemon juice. Scatter the capers and butter around the pot. If using lemon zest, add it now for extra brightness.
Cook it: Slow cooker: Cook on Low for 4–5 hours or High for 2–3 hours, until the chicken is tender and reaches 165°F.
Instant Pot: Seal and cook on High Pressure for 8–10 minutes (10–12 minutes if starting from frozen), then quick release.
Finish the sauce: Remove the chicken to a plate and tent loosely with foil.
Stir in the heavy cream and cream cheese until smooth and melted.
Thicken (optional): If you want a thicker sauce, whisk 1 tablespoon cornstarch with 1 tablespoon cold water to make a slurry. Stir it into the sauce and simmer (Sauté mode for Instant Pot, or High heat in slow cooker) for 3–5 minutes until slightly thickened. Repeat with another tablespoon if needed.
Taste and adjust: Add more salt, pepper, or lemon juice to balance the richness.
The sauce should be creamy with a pleasant tang.
Combine and serve: Return the chicken to the sauce. Spoon over pasta, rice, or mashed potatoes. Garnish with chopped parsley and extra capers if you like.