Prep the chicken: Pat the chicken dry and season both sides with salt and pepper. If using large breasts, slice them horizontally to create cutlets for quicker, more even cooking.
Heat the pan: Set a large skillet over medium-high heat.
Add olive oil (and 1 tablespoon butter if using). When it shimmers, it’s ready.
Sear the chicken: Add chicken in a single layer. Don’t crowd the pan.
Sear 4–5 minutes per side, until golden and nearly cooked through. Transfer to a plate and tent with foil.
Sauté the aromatics: Reduce heat to medium. If the pan looks dry, add a touch more oil.
Stir in garlic and cook 30 seconds until fragrant. Avoid browning.
Build the sauce: Sprinkle in the ranch seasoning and stir. Pour in chicken broth while scraping up browned bits.
Simmer 2–3 minutes to slightly reduce.
Add the cream: Lower heat to medium-low. Stir in heavy cream and Dijon. Simmer gently (small bubbles), 3–4 minutes, until the sauce lightly thickens.
Finish with cheese and lemon: Stir in Parmesan until melted and smooth.
Add lemon juice to brighten. Taste and adjust salt and pepper. If the sauce seems too thick, thin with a splash of broth.
Return the chicken: Nestle the chicken back into the skillet with any juices.
Spoon sauce over the top. Simmer 2–4 minutes, until the chicken is cooked through and reads 165°F in the thickest part.
Optional add-ins: Fold in a handful of spinach to wilt, or add sautéed mushrooms or warm broccoli. Keep the heat gentle to maintain a silky sauce.
Finish and serve: Swirl in the remaining tablespoon of butter for gloss.
Garnish with chopped parsley or chives. Serve over mashed potatoes, egg noodles, rice, or cauliflower mash.