Pound and season the chicken. If using thick breasts, lightly pound to even thickness (about ½–¾ inch). Pat dry.
Season both sides with salt and pepper.
Sear the chicken. Heat 1 tablespoon olive oil and 1 tablespoon butter in a large skillet over medium-high heat. Add chicken and sear 4–6 minutes per side until deeply golden and just cooked through (165°F internal). Transfer to a plate; tent with foil.
Sauté the mushrooms. In the same skillet, add remaining 1 tablespoon olive oil and 1 tablespoon butter.
Add mushrooms with a pinch of salt. Cook 6–8 minutes, stirring occasionally, until browned and their moisture cooks off.
Add aromatics and seasoning. Stir in minced garlic, Italian seasoning, and optional red pepper flakes. Cook 30–60 seconds until fragrant.
Scrape up browned bits from the pan as the garlic releases aroma.
Deglaze and simmer. Pour in chicken broth (and optional white wine if using). Simmer 2–3 minutes, scraping the pan, until the liquid reduces slightly.
Make it creamy. Reduce heat to medium-low. Stir in heavy cream and bring to a gentle simmer.
Cook 2–3 minutes until the sauce thickens enough to coat the back of a spoon.
Add parmesan and balance. Stir in parmesan until melted and smooth. Add 1 teaspoon lemon juice, taste, and adjust with more salt, pepper, or lemon as needed.
Return chicken to the pan. Nestle chicken into the sauce and simmer 2–3 minutes to warm through and marry flavors. Spoon sauce over the top.
Finish and serve. Sprinkle with chopped parsley.
Serve hot with your favorite low-carb sides like zucchini noodles, sautéed spinach, roasted broccoli, or cauliflower mash.