This creamy chicken casserole is a real crowd pleaser. I make it as a big batch then freeze half for a quick dinner another night.
You can cook it on the hob (stovetop) or in the oven. It reheats beautifully, and there’s plenty of sauce to soak into your mashed potato and veggies!

Close up of a large pan filled with creamy chicken and mushroom casserole. There is a wooden spoon in the pan.
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I don’t know about you, but I desperately crave creamy sauces and mashed potato whenever the weather is even marginally cold.

This is one of my favourite big batch meals to make because:

  • It’s great for feeding a crowd (easy to make for 10+ people)
  • You can make it ahead
  • It’s suitable for freezing….
  • …..which also means you can eat some for dinner and freeze some for a super quick dinner next time

📋 What do we need?

Ingredients for creamy chicken and mushroom casserole on a wooden chopping board against a light background.

📺 Watch how to make it

Full recipe with detailed steps in the recipe card at the end of this post.

👩‍🍳PRO TIP Make sure you’ve got a very large frying pan or casserole pan as this recipe is pretty big!

If your family are anything like mine when it comes to comfort food like this, you should hear lots of ‘Mmmms’ and chomping noises for the first 5 minutes, before the chatting resumes. Always the sign of a good meal!

Overhead image of creamy chicken and mushroom casserole in a large frying pan on a light background. There is a cream linen napkin and a wooden spoon next to the pan and parsley scattered in and around the pan.

I love that there’s plenty of sauce with this dish, so you’ve got enough to drizzle over your chicken, potatoes and vegetables ❤️


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4.96 from 22 votes

Creamy Chicken and Mushroom One Pan Casserole

My big batch creamy chicken and mushroom one pan casserole! Cook this dish on the hob or in the oven. Make ahead and serve later!
Prep Time: 15 minutes
Cook Time: 50 minutes
Total Time: 1 hour 5 minutes
Servings: 10 servings
Course: Dinner
Cuisine: British

Ingredients

Chicken:

  • 5 chicken breasts (1kg/2.25 lb) chopped into big chunks or strips
  • 45 g (6 tbsp) plain (all-purpose) flour
  • ½ tsp salt
  • ½ tsp black pepper

Sauce:

  • 2 tbsp oil
  • 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 1/4 cups) chicken stock
  • 300 ml (1 1/4 cups) milk whole milk or half-fat
  • 2 tbsp freshly squeezed lemon juice juice of approx. 1 lemon
  • 20 chestnut mushrooms thickly sliced
  • ½ tsp salt
  • ½ tsp pepper
  • 240 ml (1 cup) double (heavy) cream
  • 2 tbsp cornflour mixed with 5 tbsp cold water – to make a slurry, (cornstarch in USA) **Optional**
  • small bunch parsley chopped

Serve with:

  • mashed potatoes
  • sprouts
  • peas
  • sweetcorn
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Instructions 

  • Place the chicken in a bowl with the flour, salt, and pepper. Toss to cover the chicken in the flour and seasoning.
    5 chicken breasts, 45 g (6 tbsp) plain (all-purpose) flour, 1/2 tsp salt, 1/2 tsp black pepper
  • Heat the oil over a high heat in a large frying pan (skillet) and working in 2 batches, add the chicken. Brown all over (it doesn't need to be cooked through at this point). Remove from the pan with a slotted spoon and put to one side.
    2 tbsp oil
  • Place the butter in the same frying pan and melt over a low-medium heat. Add the onions, garlic, thyme, and celery salt and cook for 5 minutes until the onion softens. Sprinkle on the flour and stir for a minute (it will be lumpy).
    2 tbsp unsalted butter, 3 small-to-medium onions, 5 cloves garlic, 1 tsp dried thyme, ½ tsp celery salt, 25 g (3 tbsp) plain (all-purpose) flour
  • Pour in a splash of the stock and stir, using a whisk until combined. Continue to add in stock, a little at a time, whilst stirring, until all the stock is added and you have a smooth sauce with no lumps (the onions will still be in there though – so it will look a little lumpy because of that).
    1 litre (4 1/4 cups) chicken stock
  • Add the milk and continue to stir over the heat until the sauce thickens, then add in the lemon juice.
    300 ml (1 1/4 cups) milk, 2 tbsp freshly squeezed lemon juice
  • Add the mushrooms, the cooked chicken and the salt and pepper. Place a lid on the pan and simmer gently on the hob for 20 minutes.
    20 chestnut mushrooms, 1/2 tsp salt, 1/2 tsp pepper
  • **Alternatively you can transfer to a casserole dish at this point. Cover with foil and place in the oven at 175C/350F (fan) for 30 minutes**
  • Remove the lid and stir in the cream, then heat through for a further 5 minutes (place back in the oven if oven cooking).
    240 ml (1 cup) double (heavy) cream
  • If you'd like the sauce to be any thicker, then at this point you can stir in the cornflour slurry. Add a little splash at a time, whilst stirring, until you get the thickness you want.
    2 tbsp cornflour
  • Serve the casserole with vegetables (I like to serve mine with mashed potatoes, sprouts, peas and sweetcorn) and a sprinkling of parsley.
    small bunch parsley, mashed potatoes, sprouts, peas, sweetcorn

Video

Notes

Make Ahead:
You can make this dish ahead, then cool, cover and refrigerate for a day.
Heat through thoroughly in the oven (covered) at 175C/350F for approx 20-25 minutes. Or heat through on the hob for 10-15 minutes on a medium heat until the chicken is hot all the way through.
Add a splash of cream or milk if needed to loosen it up.
Freezing:
Make the casserole, then cool, cover and freeze. Defrost thoroughly in the refrigerator and heat through thoroughly in the oven (covered) at 175C/350F for approx 20-25 minutes. Or heat through on the hob for 10-15 minutes on a medium heat until the chicken is hot all the way through.
Reducing the quantities:
You can halve the quantities if necessary – no change to the cooking times. 
Can I make it in the slow cooker?
I haven’t tried this one in the slow cooker yet. If you try it, please let me know how it went. I’ll update the notes when I test it using the slow cooker.
Nutritional Information is approx. per serving WITHOUT Serving suggestion of Mash Potato, Sprouts, Peas and Sweetcorn.

Nutrition

Calories: 315kcal | Carbohydrates: 13g | Protein: 25g | Fat: 18g | Saturated Fat: 8g | Polyunsaturated Fat: 2g | Monounsaturated Fat: 6g | Trans Fat: 0.1g | Cholesterol: 101mg | Sodium: 887mg | Potassium: 692mg | Fiber: 1g | Sugar: 5g | Vitamin A: 511IU | Vitamin C: 5mg | Calcium: 84mg | Iron: 1mg

Nutrition information is automatically calculated, so should only be used as an approximation.

This post was first published in September 2017, then updated Feb 2019 and again in February 2023 with new images, recipe video and a bit of housekeeping.

Some of the links in this post may be affiliate links – which means if you buy the product I get a small commission (at no extra cost to you). If you do buy, then thank you! That’s what helps us to keep Kitchen Sanctuary running. The nutritional information provided is approximate and can vary depending on several factors. For more information please see our Terms & Conditions.

Welcome to Kitchen Sanctuary

Hi, I'm Nicky and I love to cook! I want to share with you my favourite, delicious family friendly recipes. I want to inspire you to create fantastic food for your family every day.

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Comments

  1. Ravon G. says:

    5 stars
    I am a cook at a senior assistant living facility and this was a hit with the residents. Not too salty but not bland. A perfect blend of flavors.