Preheat your oven to 375°F and lightly grease a 9x13-inch baking dish. Pat your chicken pieces dry with paper towels to ensure they brown properly during the initial cooking phase.

Heat butter in a large skillet over medium-high heat and sauté the diced onion, minced garlic, sliced mushrooms, and diced celery for 5-7 minutes until softened and fragrant. This aromatic base infuses the entire golden tender chicken stuffing casserole with incredible depth and flavor.

Stir in the dried thyme, dried sage, salt, and black pepper, cooking for another minute until blooming and fragrant. Add the beaten eggs and heavy cream to the vegetable mixture, stirring well to combine all ingredients thoroughly.

In a separate large bowl, combine the stuffing mix with chicken broth, mixing until the stuffing reaches a moist but not soggy consistency. Fold in the vegetable and egg mixture gently, being careful not to overmix the delicate ingredients together.

Spread half of the stuffing mixture onto the bottom of your prepared baking dish, creating an even layer. Arrange the chicken pieces on top in a single layer, then cover completely with the remaining stuffing mixture.

Cover the baking dish tightly with aluminum foil and bake for 25 minutes at 375°F to ensure the chicken cooks through completely.

Remove the foil and bake uncovered for an additional 10 minutes until the top turns golden brown and crispy. The chicken stuffing casserole should reach an internal temperature of 165°F when measured with a meat thermometer in the thickest piece.