Preheat the oven to 200°C.
Season the chicken legs with salt and pepper.
Cut the leeks into 5-6 cm pieces (discard the green part).
Heat the oil in frying a pan and fry the chicken on each side for 2-3 minutes until light brown, then place them in a roasting dish (skin side up).
Put the frying pan back on the stove and pour in the wine. Let it bubble for 5 minutes.
Add the bay leaves, thyme leaves, garlic & the leek chunks and sauté for a further 5 minutes. Transfer this to the roasting dish, arranging the leek pieces around the chicken. Cover with foil, then bake for 30 minutes.
Remove the foil and bake for another 20-30 minutes, until golden.
Transfer the chicken and leek to a serving dish.
Add the mustard and parsley to the sauce, then pour this over the chicken & leek.
Serve warm.