Preheat the oven to 180C/350F/Gas 4.
For the sea bass, place the flour, salt, egg yolk and herbs into the bowl of a food processor and pulse until combined. Add a little cold water if required and continue to pulse until a dough forms.
Roll out the pastry on a floured surface and wrap the sea bass in it. Press the edges of the pastry together to seal. Transfer to a baking sheet and cook in the oven for 12-15 minutes, or until the pastry crust is golden-brown and the fish is completely cooked through.
For the turmeric potatoes, place the potatoes and turmeric in a pan of water and bring to the boil. Cook the potatoes until tender, about 8-10 minutes, and then drain.
To serve, place the pastry-crusted fish onto a large serving plate and open up the pastry crust to reveal the cooked fish inside. Arrange the potatoes around the edge and garnish with the parsley sprigs and lemon wedges.