When it comes to hearty, comforting meals that satisfy the entire family, a garlic mushroom chicken casserole is a true standout. This dish combines tender chunks of chicken with earthy mushrooms, creamy garlic sauce, and a medley of aromatics, making it perfect for a wholesome dinner. Ideal for large gatherings or meal prepping for the week, this casserole is both versatile and indulgent, offering a rich, savory flavor profile that pairs perfectly with mashed potatoes, roasted vegetables, or simple green sides.
This recipe is designed to be approachable while still delivering restaurant-quality results. The creamy sauce, infused with garlic and thyme, envelops each piece of chicken and mushroom, ensuring every bite is juicy, flavorful, and satisfying. With a little preparation, you can cook this dish on the stove top or in the oven, making it adaptable for any kitchen setup or timeline.
Why You’ll Love This Garlic Mushroom Chicken Casserole
There are a few key reasons why this casserole has become a family favorite:
- Flavor-packed: Garlic, thyme, and sautéed onions create a base of incredible aroma and taste.
- Creamy and hearty: The sauce is rich and velvety, perfect for pairing with mashed potatoes or crusty bread.
- Flexible cooking methods: Can be made on the stovetop or baked in the oven.
- Make-ahead friendly: Prepares easily in advance and freezes well, perfect for busy weeknights.
- Feeds a crowd: Generous portions make it suitable for 8–10 servings, ideal for family dinners or entertaining.
By following this recipe, you’ll have a dish that’s both impressive and comforting, a true centerpiece for any dinner table.
Ingredients for Garlic Mushroom Chicken Casserole (Serves 10)
Chicken
- 5 chicken breasts (approx. 1 kg / 2.25 lb), cut into large chunks or strips
- 45 g (6 tbsp) plain all-purpose flour
- ½ tsp salt
- ½ tsp black pepper
Sauce
- 2 tbsp oil (vegetable, sunflower, or canola)
- 2 tbsp unsalted butter
- 3 small-to-medium onions, peeled and finely diced
- 5 cloves garlic, peeled and minced
- 1 tsp dried thyme
- ½ tsp celery salt (optional)
- 25 g (3 tbsp) plain all-purpose flour
- 1 litre (4 ¼ cups) chicken stock
- 300 ml (1 ¼ cups) milk (whole or half-fat)
- 2 tbsp freshly squeezed lemon juice (approx. 1 lemon)
- 20 chestnut mushrooms, thickly sliced
- ½ tsp salt
- ½ tsp black pepper
- 240 ml (1 cup) double cream (heavy cream)
- 2 tbsp cornflour mixed with 5 tbsp cold water to make a slurry (optional for thicker sauce)
- Small bunch parsley, chopped for garnish
Suggested Sides
- Mashed potatoes
- Roasted sprouts
- Steamed peas
- Sweetcorn
Step-by-Step Instructions
Step 1: Prepare the Chicken
Place the chopped chicken pieces in a large mixing bowl. Add the 6 tablespoons of flour, ½ teaspoon salt, and ½ teaspoon black pepper. Toss thoroughly so that each piece of chicken is evenly coated in flour and seasoning. This helps the chicken brown beautifully and thickens the sauce slightly as it cooks.
Step 2: Brown the Chicken
Heat 2 tablespoons of oil in a large frying pan or skillet over high heat. Working in two batches to avoid overcrowding, add the chicken pieces and sear until golden on all sides. The chicken does not need to cook through at this stage. Remove the browned chicken using a slotted spoon and set aside.
Step 3: Sauté Aromatics
In the same pan, reduce the heat to medium. Add 2 tablespoons of butter and allow it to melt. Stir in the finely diced onions, minced garlic, dried thyme, and optional celery salt. Cook for approximately 5 minutes, stirring occasionally, until the onions are soft and fragrant.
Step 4: Make the Base Sauce
Sprinkle 3 tablespoons of flour over the softened onions and garlic, stirring constantly for 1–2 minutes. This will form a roux, which thickens the sauce. Gradually add a splash of chicken stock, whisking continuously to avoid lumps. Continue adding the stock slowly until the full litre is incorporated and the sauce is smooth.
Step 5: Incorporate Milk and Lemon
Pour in 1 ¼ cups of milk and continue stirring over medium heat. Allow the sauce to thicken slightly. Once thickened, stir in 2 tablespoons of freshly squeezed lemon juice to brighten the flavors. Taste and adjust seasoning with additional salt or pepper as needed.
Step 6: Add Mushrooms and Chicken
Add the sliced mushrooms and browned chicken back into the pan. Season with ½ teaspoon salt and ½ teaspoon pepper. Place a lid on the pan and simmer gently on the stove for 20 minutes. The mushrooms will release their earthy flavor into the sauce, while the chicken finishes cooking to tender perfection.
Optional Oven Method: Transfer the mixture to a casserole dish, cover with foil, and bake at 175°C / 350°F (fan oven) for 30 minutes.
Step 7: Finish with Cream
Remove the lid and stir in 1 cup of double cream. Heat gently for an additional 5 minutes on the stove, allowing the sauce to become rich and silky. If you prefer a thicker consistency, slowly add the cornflour slurry a little at a time while stirring until the desired thickness is achieved.
Step 8: Garnish and Serve
Sprinkle chopped parsley over the finished casserole for a touch of color and freshness. Serve hot with mashed potatoes, roasted sprouts, steamed peas, and sweetcorn. The creamy sauce is perfect for drizzling over vegetables and potatoes.
Tips for Success
- Large Pan: Use a very large frying pan or casserole dish to ensure everything cooks evenly.
- Make Ahead: This dish can be prepared in advance. Cool, cover, and refrigerate for up to a day. Reheat thoroughly in the oven at 175°C / 350°F for 20–25 minutes or on the stovetop over medium heat for 10–15 minutes. Add a splash of milk or cream if the sauce thickens too much.
- Freezing: Allow the casserole to cool completely, then cover and freeze. Defrost overnight in the refrigerator and reheat thoroughly.
- Reducing Quantities: Halve the ingredients for a smaller portion; cooking times remain similar.
- Slow Cooker Option: While not tested, the casserole may be adapted for slow cooker use by combining all ingredients and cooking on low for 4–6 hours.
Why This Garlic Mushroom Chicken Casserole Is Perfect for Dinner
This casserole is perfect for a family dinner for several reasons. It combines protein, vegetables, and creamy richness into one cohesive dish, minimizing preparation and cleanup. The garlic and mushrooms add depth, while the creamy sauce ensures the meal is comforting without being overly heavy. Leftovers reheat beautifully, making it practical for busy evenings or batch cooking for the week.
Variations
- Vegetables: Swap mushrooms for a mix of mushrooms and spinach, or add bell peppers for color and sweetness.
- Cheese: Stir in grated parmesan or cheddar for a cheesy twist.
- Herbs: Fresh thyme or rosemary can be added at the end for an aromatic lift.
- Lighter Version: Replace heavy cream with half-and-half or milk for a lighter sauce.
