For the pasta dough, tip the flour and salt into a large mixing bowl and make a well in the middle. Add some of the beaten egg yolks, all of the olive oil and the water and slowly mix the ingredients together, adding more beaten egg as necessary to make a smooth dough (you may not need all of the egg).
Shape the dough into a ball and turn out onto a floured work surface. Knead the dough for 10-15 minutes, or until smooth and elastic. Shape into a ball, cover with cling film and leave to rest in the fridge for one hour.
For the filling, heat the olive oil in a pan and fry the onion and garlic over a medium-low heat for 8-10 minutes, or until softened and golden-brown. Add the mushrooms and the thyme and fry for a further 2-3 minutes, or until the mushrooms are tender. Transfer the mixture to a bowl and set aside until needed.
Place three-quarters of the chopped chicken breast meat into a food processor along with the egg and cream and blend until smooth to make a mousse. Add the chicken mousse to the bowl with the mushrooms and remaining chopped chicken and mix well to combine. Set aside.
Remove the pasta dough from the fridge and divide into four equal pieces. Cover the other three pieces with a clean, damp tea towel and dust the fourth piece in flour.
Flour the pasta machine. Starting at the lowest (thickest) setting, feed the dough through the machine, turning the handle with one hand and holding the dough as it comes through the machine with the other. Change the setting on the pasta machine to the next-thickest setting, flour it again and feed the pasta sheet through the machine again, as before, until the dough has reached the desired thickness (about 1-2mm thick). Repeat with the remaining dough until you have four sheets of thin pasta.
Lay one sheet of pasta on a floured work surface and place spoonfuls of the filling on top, ensuring there is at least an inch of space between and around each spoonful. Lay a second sheet of pasta on top and seal the edges, making sure that there are no air bubbles trapped in between the layers. Cut out the individual ravioli with a pasta wheel. Place on a floured tray, cover and refrigerate until ready to cook. Repeat with the remaining sheets of pasta and the filling until all are used up.
For the sauce, heat the olive oil in a pan and fry the onion for 10-15 minutes, or until softened and golden-brown. Season with salt and freshly ground black pepper, add the chopped shallots, garlic and wine and cook for 3-4 minutes, or until some of the alcohol has evaporated. Stir in the cream and add the tarragon, then remove from the heat.
For the spinach, melt the butter in a pan until foaming, then add the spinach and fry for 1-2 minutes, or until wilted. Season with salt and a pinch of nutmeg.
To cook the pasta, bring a large pan of salted water to just below the boil and gently cook the ravioli, in batches, for 4-5 minutes with the lid on the pan, until the pasta is al dente. Drain.
To serve, spoon the spinach into serving bowls and place the ravioli on top. Spoon over the sauce.
