Cut the swede, carrots, celery and turnips into batons.
Cut the parsnips to 5cm (2in) pieces and then slice into batons.
De-bone the chicken (if preferred).
Sprinkle the chopped onion and bay leaf in a large saucepan, cover with 1.2 litres (2 pints) of water and bring to a rapid simmer.
Season the chicken legs with salt and pepper and sit them in a steamer skin-side up. Place over the simmering water and cover with a lid. Cook for 25 minutes.
After 15 minutes, remove the chicken legs and add the carrots, swede and celery to the steaming water. Bring to the simmer again before returning the chicken legs to steam.
Continue to steam for a further five minutes.
Remove the chicken legs and keep them warm within the steamer. Strain the vegetables from the pan, discarding the bay leaf and saving the liquor in a separate saucepan. Simmer.
Arrange the vegetables in a bowl. De-skin the chicken and place on top.
Whisk the butter into the simmering cooking liquor and add a squeeze of lemon juice.
Finish with the torn parsley, then pour over the chicken and vegetables and serve.