Creamy chicken and mushroom casserole made in one pan with tender chicken breasts, a rich garlic and thyme sauce, and hearty chestnut mushrooms. This easy dinner recipe is perfect for busy weeknights or batch cooking. Serve with mashed potatoes and vegetables for a comforting family meal ready in under an hour.

This hearty chicken and mushroom casserole is a one-pan comfort food classic. Featuring tender chicken, a creamy herb-infused sauce, and plenty of mushrooms, it’s perfect for weeknight dinners or make-ahead meals. No need for multiple pots—everything comes together in one pan for minimal cleanup and maximum flavor.

Table of Contents

Ingredients

For the Chicken:

5 chicken breasts (1kg / 2.25 lbs), cut into large chunks or strips
45 g (6 tbsp) plain (all-purpose) flour
½ tsp salt
½ tsp black pepper

For the Sauce:

2 tbsp oil
2 tbsp unsalted butter
3 small to medium onions, finely diced
5 garlic cloves, minced
1 tsp dried thyme
½ tsp celery salt (optional)
25 g (3 tbsp) plain (all-purpose) flour
1 litre (4¼ cups) chicken stock
300 ml (1¼ cups) milk (whole or semi-skimmed)
2 tbsp freshly squeezed lemon juice (about 1 lemon)
20 chestnut mushrooms, thickly sliced
½ tsp salt
½ tsp black pepper
240 ml (1 cup) double (heavy) cream
2 tbsp cornflour mixed with 5 tbsp cold water (optional, for thickening)
Small bunch of parsley, chopped

To Serve:

Mashed potatoes
Sprouts
Peas
Sweetcorn

Instructions

In a large bowl, toss the chicken pieces with flour, salt, and pepper until well coated.
Heat oil in a large frying pan over high heat. In two batches, sear the chicken until golden on all sides (they don’t need to be fully cooked). Remove and set aside.
In the same pan, melt the butter over medium heat. Add onions, garlic, thyme, and celery salt. Cook for 5 minutes until softened.
Stir in the flour and cook for 1 minute. The mixture will be thick.
Gradually whisk in the chicken stock, a little at a time, to avoid lumps. Once smooth, add the milk and cook until the sauce thickens.
Stir in the lemon juice. Add mushrooms, cooked chicken, salt, and pepper.
Cover with a lid and simmer gently on the stove for 20 minutes.
Alternatively, transfer to a casserole dish, cover with foil, and bake at 175°C (350°F) for 30 minutes.
Remove the lid and stir in the cream. Cook for an additional 5 minutes.
If you prefer a thicker sauce, stir in the cornflour slurry gradually until the sauce reaches the desired consistency.
Finish with a sprinkle of chopped parsley and serve with your favorite vegetables and mashed potatoes.

Tips

Cut chicken evenly to ensure it cooks at the same rate.
Use floury potatoes for mash that pairs well with the creamy sauce.
Whisk continuously when adding stock to avoid lumps in the sauce.
Add lemon juice after the milk to prevent curdling.

Variations and Substitutions

Chicken thighs can be used instead of breasts for extra tenderness.
Vegetarian option: Replace chicken with pan-fried mushrooms or tofu, and use vegetable stock.
Low-dairy: Swap heavy cream for oat or almond cream and use plant-based butter.
Add-ins: Stir in baby spinach or green beans near the end of cooking for extra vegetables.

FAQs

Can I make this in advance?
Yes. Prepare the casserole, cool it fully, then refrigerate. Reheat gently on the stove or in the oven until piping hot.

Can I freeze it?
Cream-based sauces may separate after freezing, but you can freeze the casserole without the cream, then stir it in fresh when reheating.

Can I use pre-cooked chicken?
Yes. Skip the browning step and add cooked chicken directly to the sauce before simmering.

Serving Suggestions

Perfect over creamy mashed potatoes.
Pair with seasonal vegetables like peas, sprouts, or roasted carrots.
Great with crusty bread for mopping up the sauce.

Why You’ll Love This Recipe

One-pan recipe with easy cleanup.
Family-friendly and filling.
Creamy, savory, and loaded with comforting flavors.
Flexible—easy to adapt for dietary needs or ingredients on hand.