Heat the oil in a large casserole dish. Brown the chicken until golden on all sides - you might have to do this in batches - remove the chicken from the pan as you go and set aside.
Add the lardons to the pan and sizzle for a few mins, then add the onion, celery and leeks, and cook over a medium heat for 8-10 mins until the vegetables have softened. Stir in the flour, season and cook for a further 2 mins.
Gradually stir in the wine and allow it to bubble away, then stir in the stock. Return the chicken to the pan with the bay leaves and cover with a lid. Reduce the heat and simmer gently for 1½ hrs or until the chicken is tender. The stew can now be cooled and frozen if you’re making ahead. Just defrost thoroughly, then gently warm through back in the pan before continuing.
Heat oven to 200C/180C fan/gas 6. Add the peas, sundried tomatoes, pesto and basil to the stew. To make the dumplings, rub the butter into the flour until it resembles fine breadcrumbs. Mix in the grated cheese and add 150ml water, mixing with a cutlery knife to bring the crumbs together to form a light and sticky dough. Break off walnut-sized lumps and shape into small balls. Roll the tops of the dumplings in the pine nuts so a few stick to the outside, then place the dumplings on top of the stew and scatter with any remaining nuts. Put the dish in the oven and bake for 25 mins until the dumplings are golden brown and cooked through. Serve with mashed potato and extra veg if you like.