Creating Chicken Fricassee can be straightforward if you follow these step-by-step instructions:

1. Heat the Oil: In a large skillet or Dutch oven, heat the olive oil and butter over medium heat.
2. Sear the Chicken: Season the chicken thighs with salt and pepper, then add them to the pan skin-side down. Sear for about 5-7 minutes until golden brown, then flip and cook for an additional 5 minutes. Remove the chicken from the pan and set aside.
3. Sauté Vegetables: In the same pan, add the chopped onion, garlic, carrots, and celery. Sauté until the vegetables are tender, about 5 minutes.
4. Add Mushrooms: Stir in the sliced mushrooms and cook for another 3-4 minutes until they become tender.
5. Create the Sauce: Pour in the chicken broth, then add the Dijon mustard, thyme, bay leaf, and more salt and pepper. Bring to a simmer.
6. Return the Chicken: Place the seared chicken thighs back into the skillet, skin-side up. Cover and simmer for 20-25 minutes, or until the chicken is cooked through.
7. Add Cream: Stir in the heavy cream and cook an additional 5 minutes until the sauce thickens slightly and is creamy.
8. Adjust Seasoning: Taste and adjust seasoning as necessary, adding more salt, pepper, or thyme to your liking.
9. Garnish and Serve: Remove the bay leaf, and garnish with fresh parsley before serving.

These easy steps will lead you to a delicious Chicken Fricassee that will delight your family and friends!