For pasta: Combine all the ingredients into a food processor and blend until it forms a ball. Remove and knead for 5 minutes, cover with cling film and set aside to rest for 1 hour.
For filling: Combine together the ricotta, parmesan, lemon zest, half the parsley and seasoning. Place into a piping bag and chill until required.
Roll out the pasta dough until you have two equally long thin sheets. Cut into 12 large squares and place 6 on a floured board.
Pipe the ricotta mix into the centre of each square, forming a small nest. Place a teaspoon full of ocean trout into the nest and gently push down. Gently top with an egg yolk, brush the sides of the pasta with a little beaten egg yolk and top with a pasta square. Press down to seal well and continue until you have made 6.
Using a ring cutter, cut them into large circles and cook for 3 minutes in boiling salted water. Remove, drain and present with the lemon olive oil and chervil.