Winter chicken stew

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 leaves
• 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)