Preheat the oven to 200°C/ 180°C fan/ Gas Mark 6. In a flame-proof casserole dish heat 1 tbsp of the oil and fry the shallots or baby onions, whole, over a medium high heat until they start to turn golden brown (about 5 mins). Add the garlic and cook for a further 1 minute. Remove from the casserole and set aside.
Add the rest of the oil to the casserole and over a high heat brown the chicken on all sides. Add the onions and garlic back into the pan and pour over the wine and stock. Add the pearl barley, bay leaf, strip of lemon zest and season well with salt and pepper. Cover with the lid and bring to a simmer on the hob. Transfer to the oven and cook for 30 minutes.
Chop the carrots into large 3cm slices and add to chicken making sure that they are pushed well down into the stock. Baste the chicken with some of the stock, cover with lid and place back in the oven for another 30 minutes. Slice the leeks into large 3cm chunks and add to chicken making sure that they are pushed well down into the stock. Cook for a final 15 minutes. Once the chicken in cooked (the legs should come away easily and juices should run clear when skewer is inserted) and the broth has thickened stir through the lemon juice and chopped tarragon. Divide the chicken between 4 plates spoon over some of the vegetables and broth. Serve with some crusty bread.
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