1. Heat a large frying pan (or a casserole dish or large pan if you’re cooking the stew on the hob) for 2 mins over a medium heat, then add 1 tbsp oil and the chicken thighs, skin-side down. Fry for 8 mins, till golden brown, then turn over and fry for 5 mins to finish browning them.
2. While the chicken fries, peel and dice the onion. Trim the dry ends off the celery stick, then finely slice it. Trim, peel and dice the carrot. Thickly slice the mushrooms. From this point on, follow the method for either the slow cooker or the hob.
3. In the slow cooker^
Lift the chicken thighs out of the frying pan and add them to a 3½ ltr slow cooker. Scoop all the chopped veg into the frying pan. Season with salt and pepper and cook, stirring every so often, for 5-8 mins till the veg have softened and cooked down a little.
4. While the veg fry, peel and roughly chop the potatoes. Add the veg and the potatoes to the slow cooker (see our tip on cooking the spuds). Peel and crush the garlic and add that to the slow cooker too. Season with a pinch of salt and pepper.
5. Tip in the chopped tomatoes. Half-fill the tin with water (around 200ml) and pour that into the slow cooker. Drop in the bouquet garni, pop on the lid and cook the stew on medium for 6 hrs, or cook for 8-10 hrs on low, or 4-6 hrs on high.
6. Taste the stew and add a pinch more salt and pepper if you think it needs it. Lift out the bouquet garni and discard it. Ladle the stew into deep, warm bowls and serve.
7. On the hob^
Lift the chicken out of the pan and set aside on a plate. Add the chopped veg to the pan . Season with a pinch of salt and pepper. Fry for 5 mins, stirring often, till the veg have started to soften.
8. While the veg fry, peel and roughly chop the potatoes. Peel and crush the garlic.
9. Stir the garlic into the chopped veg. Stir the potatoes into the veg. Add the chicken back to the pan, tipping in any juices from the plate. Pour in the chopped tomatoes. Fill the tin with water (around 400ml) and pour that into the pan. Drop in the bouquet garni, pop on a lid and cook for 1 hr.
10. Taste the stew and add a pinch more salt and pepper if you think it needs it. Lift out the bouquet garni and discard it. Ladle the stew into deep, warm bowls and serve.