Season chicken breasts with salt and pepper.

Heat olive oil in a large skillet over medium-high heat. Add chicken breasts and cook until golden brown on both sides, about 5-6 minutes per side. Remove chicken and set aside.

In the same skillet, add onions and mushrooms. Cook until they begin to soften, about 3-4 minutes. Add garlic and cook for another minute.

Pour in the chicken broth to deglaze the pan, scraping up any brown bits from the bottom of the skillet.

Stir in heavy cream and thyme, bringing to a simmer. Reduce heat to low and return the chicken breasts to the skillet. Cover and simmer for about 10 minutes, or until the chicken is cooked through.

Garnish with chopped parsley before serving.