- 3 tbsp white wine vinegar
- 3 tbsp white wine
- 10 black peppercorns, lightly crushed
- 2 tbsp shallots, peeled, finely chopped
- 1 tsp finely chopped fresh tarragon leaves
- 1 tbsp water
- 1 tbsp tomato purée
- 3 free-range egg yolks
- 200g/7oz butter, melted
- 1 tbsp finely chopped fresh flatleaf parsley
- 2 tbsp olive oil
- 8 lemon sole fillets
- salt and freshly ground black pepper
- 1 tsp Dijon mustard
- 1 tbsp white wine vinegar
- 3 tbsp rapeseed oil
- salt and freshly ground black pepper
- 150g/5oz watercress, leaves only
- For the Choron sauce, place the white wine vinegar, white wine, black peppercorns, shallots and tarragon into a non-reactive saucepan and bring to the boil. Reduce the heat and simmer until the liquid in the pan has reduced to about 1 tablespoon.
- Add the water and tomato purée to the pan and whisk to combine. Beat in the egg yolks, whisking for 3-4 minutes over a low heat, or until frothy. Gradually pour in the butter in a thin, steady stream, whisking continuously until all of the butter has been incorporated and the sauce is thickened.
- Season, to taste, with salt and freshly ground black pepper, then strain the sauce through a fine sieve. Discard the solids left behind in the sieve. Keep warm until ready to serve. Stir the parsley into the sauce just before serving.
- Preheat the grill to high. Lightly grease a roasting tray with olive oil.
- For the lemon sole, place the sole fillets skin-side up onto the prepared roasting tray and season with salt and freshly ground black pepper. Grill for 3-4 minutes, or until the skin is crisp and golden-brown and the fish is cooked through. (When the fish is cooked, the flesh should be opaque all the way through and flake easily with a fork.) Remove the fish from the grill and set aside to rest for 1-2 minutes.
- For the watercress, whisk the Dijon mustard, white wine vinegar and rapeseed oil together in a small bowl until emulsified. Season, to taste, with salt and freshly ground black pepper. Place the watercress in a bowl, pour over the dressing and toss well to coat.
- To serve, place 2 fillets on each serving plate. Arrange the watercress alongside, then spoon the Choron sauce over the fish.