Chicken and vegetable stew recipe

Name: Chicken and vegetable stew recipe
Ingredients: 1 tbsp sunflower oil; 1 onion, finely chopped; 4 garlic cloves, sliced; 1.4l hot chicken stock; 1 large potato, finely grated; 1 tbsp fresh thyme leaf; 2 tsp fresh rosemary leaves; 2 x 850g family packs skinless chicken thighs (count the number in the pack- you need 16 in total); 6 carrots, halved lengthways and cut into chunks; 2 parsnips, halved lengthways and cut into chunks; 3 leeks, well washed and thickly sliced; mash and peas, to serve (optional)