Preheat the oven to 200°C/180°C fan/ Gas 6. Slice the top off the garlic bulb, place onto a baking tray and drizzle with oil, then roast for 20 minutes.
Heat a splash of oil in a large saucepan and fry the shallots. After 5 minutes, add the mushrooms and cook for another 3-5 minutes until golden.
Meanwhile, heat a drizzle of oil in a large frying pan. Season the chicken and brown on all sides. Add the chicken to the saucepan with the shallots and mushrooms. Pour in the wine and cook for 5 minutes, before adding the thyme and stock. Bring to the boil then simmer for 45 minutes to an hour until the chicken is cooked through with no pink showing.
Add the Worcestershire sauce and then mix the cornflour with a little water and whisk into the casserole and cook for another 5 minutes.
To make the mash, boil the potatoes for 20 minutes then drain. Take the garlic and squeeze the cooked insides into the potatoes then mash with a glug of olive oil and the milk. Season to taste. Serve with the casserole.
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