Season the chicken breasts with salt and pepper.
Heat olive oil in a large skillet over medium-high heat.
Add chicken breasts and cook until golden and cooked through, about 5-7 minutes per side. Remove and set aside.
In the same skillet, add garlic and sauté until fragrant, about 1 minute.
Add mushrooms and cook until softened and browned, about 5 minutes.
Pour in chicken broth and bring to a simmer, scraping up any browned bits from the pan.
Stir in heavy cream if using, and cook until the sauce thickens slightly.
Return chicken to the skillet and spoon sauce over the top. Cook for another 2 minutes to heat through.
Garnish with fresh parsley before serving.