Pre-heat the oven to 190°C/170°C fan/gas mark 5.
Pour the olive oil into a large casserole pot or saucepan and heat until the oil starts smoking.
Season both sides of the chicken pieces with the salt and pepper and place into the pot in a single layer. Cook for 3-4 minutes on both sides until the chicken has browned. Then remove the chicken and set aside for now.
Add the onions and celery into the cooking pot and cook for 10 minutes until the vegetables start to turn translucent.
Add in the carrots, cubed swede, herbs, garlic, mustard, redcurrant jelly, Worcestershire sauce, chicken stock and stir together. Add the chicken back in, tucking under the liquid. Place the lid on the pot and transfer to the oven. Bake for 50 minutes. Then remove from the oven and place back on the hob on a very low heat.
Remove the cooked chicken pieces from the casserole pot using a pair of tongs and place into a bowl.
Make the cornflour slurry by whisking the cornflour with the cold water until smooth.
Add the slurry into the casserole along with the green beans and bring the casserole up to a gentle boil.
Shred the chicken with two forks into the bowl until you achieve bite sized pieces.
Add the chicken back into the casserole, the sauce should now have thickened because of the cornflour, and cook for a final 5 minutes.
Remove the stems of fresh herbs and the bay leaves.
Serve the casserole sprinkled with fresh parsley.