1. Preheat your oven to 375°F or 190°C.

2. Cook diced bacon in a large skillet over medium heat until crispy, then remove it from the skillet and set it aside on a paper towel-lined plate.

3. Add chopped onion to the skillet and cook until softened, this should take about 5 minutes.

4. Next, add the mushrooms to the skillet and cook until they release their liquid and start to brown, which should take about 5 minutes.

5. Add chicken broth, salt, and pepper to the skillet, stirring to combine, then bring the mixture to a simmer and cook for 2 minutes.

6. In a large bowl, whisk together heavy whipping cream and soy sauce.

7. Add cooked chicken breasts to the bowl and toss to coat, then add the cooked mushroom mixture, chopped parsley, and crispy bacon to the bowl, stirring to combine.

8. Grease a 9x13-inch or 23x33-centimeter baking dish with butter and add the chicken and mushroom mixture.

9. Bake in the preheated oven for 35-40 minutes, or until the casserole is hot and the chicken is cooked through.

10. Serve hot, garnished with roasted root vegetables such as carrots and parsnips.