- Preheat the oven to 190C/375F/Gas 5.
- Heat a griddle pan until very hot.
- Season the fish with salt and black pepper and place onto the griddle pan for one minute until just marked.
- Remove the fish and turn 90 degrees before placing it back on the griddle pan (this will create a criss-cross griddled appearance).
- Cook for a further minute then place the whole griddle pan into the oven for 8-10 minutes until cooked through.
- Remove and place on a serving plate
- For the Sauce
- Melt the butter in a small saucepan over medium-low heat. Add garlic and shallots; cook and stir until transparent, about 3 minutes.
- Season with tarragon, salt and white pepper.
- Increase the heat to medium, and stir in the white wine and lemon juice.
- Bring to a simmer, then whisk for 1 minute. Remove from the heat and sprinkle in parsley.
- Pour over your favorite white fish before serving.
Serve with parsnip crisps, broad beans, lemon, a small but interesting mixed salad and rice.