Step 1

Place the chicken in a bowl with 6 tablespoons of the flour plus 1/2 tsp each of salt and pepper. Toss to cover the chicken in the flour and seasoning.

Step 2

Heat the oil over a high heat in a large frying pan (skillet) and 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.

Step 3

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 remaining 3 tbsp of flour and stir for a minute (it will be lumpy).

Step 4

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).

Step 5

Add the milk and continue to stir over the heat until the sauce thickens, then add in the lemon juice.

Step 6

Add the mushrooms, the chicken and the remaining 1/2 tsp of salt and pepper. Place a lid on the pan and simmer gently on the hob for 20 minutes.

Step 7

**Alternatively you can transfer to a casserole dish at this point. Cover with foil and place in the oven at 175C/350F for 30 minutes**

Step 8

Remove the lid and stir in the cream, then heat through for a further 5 minutes (place back in the oven if oven cooking).

Step 9

Remove the lid and test for seasoning. Add a little more salt and pepper if needed.

Step 10

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.

Step 11

Serve the casserole with vegetables (I like to serve mine with sprouts, peas and sweetcorn) and a sprinkling of parsley.