For the plaice, warm the white wine in a saucepan, then add the sultanas and set aside to soak for a couple of minutes.
Drain the raisins, reserving the wine and set aside.
For the cauliflower purée, cook the cauliflower florets in a pan of salted boiling water for 4-5 minutes, or until just tender.
Drain the cauliflower and blend in a blender with the butter and cream until smooth. Season with salt and freshly ground black pepper and keep warm.
For the butter sauce, heat the shallot, vinegar and reserved white wine in a saucepan until boiling. Continue to cook until the volume of the liquid is about two tablespoons. Add the water and continue to cook until the volume of the liquid is one tablespoon.
Reduce the heat and whisk in the butter, a cube at a time, until well combined. Pass the sauce through a sieve into a clean saucepan and season with salt and freshly ground black pepper.
Season the plaice with a little salt.
Melt the butter for cooking the plaice in a frying pan until foaming, add the plaice fillets, presentation-side down and cook for 1-1½ minutes, or until just cooked. Turn over and cook for another 45 seconds.
Remove the plaice fillets from the pan and set aside to rest for a couple of minutes.
To serve, spoon the cauliflower purée into the centre of serving plates. Top each plate with two of the plaice fillets and spoon the soaked raisins around the edge.
Spoon the butter sauce over them and finish with a scattering of the mustard frills.