Cut a small cross into the bottom of the tomato with a small, sharp knife and blanch in a pan of boiling water for about ten seconds, then drain and plunge into ice-cold water. Peel the tomato and discard the skin.
Cut the peeled tomato into quarters and remove the seeds. Pat the tomato pieces dry with a clean tea towel and cut into small dice. Set aside.
Heat a frying pan over a medium heat and add the potted shrimps, shallots and tomato. Cook for 5–7 minutes until the butter has melted into a sauce. Stir in the herbs and capers and keep warm.
For the potatoes, bring a pan of water to the boil and cook the potatoes for 6–8 minutes, or until tender,
Drain the potatoes and return them to the pan to air-dry for a couple of minutes. Gradually add the cream and butter and mix with a hand-held blender until smooth. Grate in the nutmeg and season. Cover with greaseproof paper and keep warm.
For the hake, preheat the grill to medium-high. Heat the vegetable oil in a pan until smoking point, season the skin side of the hake with sea salt and the flesh side with salt and the Espelette pepper. Cook skin-side down in the pan for 1–2 minutes. Place the pan under the grill for 2–3 minutes or until the fish is slightly translucent.
Add a knob of butter to the pan, turn over the fish fillets and baste with the melted butter.
Heat the remaining butter in a pan set over a high heat. Add the spinach and wild garlic leaves and cook for 1 minute.
Serve the hake with the pommes mousseline, wilted greens and the shrimp sauce spooned over the top. Garnish with lemon zest, slices and chervil cress and wild garlic flowers, if using.