Pre-heat oven to 190 C. In a heavy based frying pan, heat oil until just hot, but not smoking. Gently place cod, skin side down in the pan and allow the skin to rest into the oil. Forcing the fish will peel away the skin from the flesh.

Arrange French onions around the pieces of fish, cut face down, which will allow the onions to caramelise while cooking.

Place the whole frying pan into the oven for about 8 minutes. Remove and place back onto the heat, gently flipping the fish over onto the flesh and adding butter and thyme to the pan.

As the butter melts, shake the pan to release the onions, squeeze in lemon and carefully spoon the foaming butter over the fish.

Remove the fish and onions and place on some paper towel to set aside for plating.

Sauce Soubise:

Heat olive oil in a heavy-based saucepan and add finely sliced onions, garlic and thyme. The objective is to cook the onions without any colour, until they are translucent and soft. This can be achieved by adding the white wine and covering the saucepan with a solid lid.

Once the onions have softened, add the fish stock and reduce the liquid by one third. Finally, add the pure cream, adjust seasoning and blend sauce until smooth.

Mustard Sabayon:

Whisk egg yolks, mustard and white wine over a bain-marie until ribbon stage. Separately whisk pure cream until the same consistency has been reached. Allow the egg mixture to cool slightly and then gently fold the whipped cream into the mix. Adjust seasoning to taste.

To serve:

Pour the Sauce Soubise into a deep-style bowl, place the fish crispy ski side up in the bowl and arrange the caramelised French onions around the fish.

To finish, spoon the Mustard Sabayon over the top of the fish.

Garnish with fresh herbs such as dill, parsley and baby basil leaves.