Pre-heat oven to 200C

Finely chop the onion, garlic and celery

Cook onion and celery in a shallow pan, over a moderate heat, until softened. Add garlic and continue to cook on gentle heat

Chop avocado and add to the pan

Add stock and creme fraiche. Bring to boil and simmer for 5 minutes

Finely slice approximately 2/3 of the celeriac and put to the side. Finely chop the remainder and add to the pan. Continue to simmer for a further 5 minutes

Add the zest and half the juice from lemon.

Remove from the heat. Using a liquidiser or hand blender, blend until smooth and put to one side. (At this stage, it makes a great soup!)

Chop the fillets into smallish cubes (roughly 3-4cm)

Pour 1/2 the 'soup' into an oven proof dish. Add the green beans and fish then pour over the remaining sauce.

Arrange sliced celeriac over the top and pour the remaining juice from the lemon over the celeriac.

Great the cheese over the top and Add a few twists of black pepper. Place on middle shelf of oven. Cook for approximately 40 minutes.

Garnish with celery leaf and a few sprigs of parsley