Pat the chicken strips dry and season with 3/4 teaspoon of the salt, the pepper, and the garlic powder. Heat 2 tablespoons of the olive oil in the large skillet over medium-high heat until shimmering. Sear the chicken in a single layer, 3–4 minutes per side, until deeply golden. Work in two batches if needed — crowding steams the chicken instead of browning it. Transfer to a plate; it does not need to be fully cooked through yet.

Add the remaining 1 tablespoon olive oil to the same skillet. Add the mushrooms in a single layer — again in two batches if they don't fit — and sear undisturbed for 2–3 minutes per side until deeply browned. Season with the remaining 1/4 teaspoon salt. Transfer to the plate with the chicken. Deep browning is where the flavor lives; pale, steamed mushrooms are the enemy here.

Reduce the heat to medium. Melt 2 tablespoons of the butter in the skillet, then add the sliced garlic and thyme. Cook, stirring constantly, 1–2 minutes until the garlic is fragrant and just turning golden at the edges — not brown, which tastes bitter.

Pour in the chicken broth, scraping up every browned bit from the bottom of the pan with a wooden spoon. Let it simmer 1–2 minutes until slightly reduced. Those browned bits are the backbone of the sauce.

Take the skillet OFF the heat. Stir in the heavy cream, then sprinkle in the Parmesan a handful at a time, stirring until melted and silky. Adding cheese off the heat keeps the sauce smooth instead of grainy or split. Return the skillet to low heat only if needed to warm through — never boil once the cream and cheese are in.

Return the chicken and mushrooms (plus any juices from the plate) to the skillet. Stir in the remaining 2 tablespoons butter until glossy. Simmer gently 1–2 minutes until the chicken is cooked through and the sauce coats a spoon. Shower with parsley and extra thyme and serve over mashed potatoes, buttered noodles, or with crusty bread.