Add the onion to the pan and cook on a low heat for 8-10 mins until tender. Then add the garlic, stirring for 1 min or so, followed by the carrot and the mushrooms, stirring for about 3 mins, until softened. Tip the turkey mince back into the pan, add the tomato purée, give everything a quick stir and tip in the chopped tomatoes. Fill 1 can with water and pour into the pan. Crumble over the chicken stock cubes and bring to the boil. Once boiling, lower the heat and simmer for about 1 hr, until the sauce has thickened and the veg is tender.