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Creamy Chicken and Mushroom One Pan Casserole Recipe

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
Calories 315kcal

Ingredients

  • 5 chicken breasts ((1kg/2.25 lb) chopped into big chunks or strips)
  • 45 g (6 tbsp) plain (all-purpose) flour
  • 1/2 tsp salt
  • 1/2 tsp black pepper
  • 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 )
  • 1/2 tsp salt
  • 1/2 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)
  • mashed potatoes
  • sprouts
  • peas
  • sweetcorn

Instructions

  • Place the chicken in a bowl with the flour, salt, and pepper. Toss to cover the chicken in the flour and seasoning.
  • 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.
  • 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).
  • 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).
  • Add the milk and continue to stir over the heat until the sauce thickens, then add in the 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.
  • **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).
  • 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.
  • Serve the casserole with vegetables (I like to serve mine with mashed potatoes, sprouts, peas and sweetcorn) and a sprinkling of parsley.

Notes

  • For perfectly cooked chicken, aim for an internal temperature of 75°C (165°F). The chicken should be golden brown on the outside but not fully cooked through before simmering.
  • To prevent the sauce from breaking, add the milk and cream gradually while stirring continuously. This helps to maintain a creamy texture without curdling.
  • If you're short on time, you can skip browning the chicken and simply add it directly to the sauce; just ensure it simmers long enough to cook through (about 20-25 minutes).
  • This casserole freezes well, so consider making a double batch. Store it in an airtight container for up to 3 months, and reheat in the oven at 175°C (350°F) until warmed through.
  • If you want to lighten the dish, substitute half of the heavy cream with Greek yogurt for a tangy twist without sacrificing creaminess.