Preheat the oven to 180C/350F/Gas 4.
Heat an ovenproof frying pan until hot, add a little vegetable oil and fry the chicken, skin-side down, until the skin is golden-brown. Transfer the pan to the oven and cook for a further 15 minutes, or until cooked through. Remove from the oven, season to taste with salt and leave to rest in a warm place.
In a bowl, whisk together the egg yolks, sugar and the vanilla seeds.
Blanch 375g/13oz of the frozen peas in a pan of salted boiling water, then drain and transfer to a blender. Pulse to a purée.
Warm the cream and puréed peas in a saucepan, then pour over the egg yolk mixture. Return the contents to the saucepan and whisk the mixture over a medium heat until it thick enough to coat the back of a spoon.
Pour into a bowl, cover the surface of the custard with cling film to prevent a skin forming and refrigerate.
Put the remaining frozen peas in a blender and pulse a couple of times to form a rough paste. Add the fresh peas, shallot and marjoram. Season with curry powder, ginger and salt, then add a little olive oil, to taste, and mix together.
To serve, dress each serving plate with a few spoonfuls of the pea custard, two chicken thighs and the pea salad. Garnish with two or three pea shoots.