Mix the ingredients for the pasta together and knead to make a dough. Wrap in plastic wrap and chill for 30 minutes.
Meanwhile, mix together the ingredients for the filling, season with salt and pepper and set aside.
For the sauce, heat the oil and butter in a small pan and add the saffron threads. Set aside to infuse while you make the ravioli.
Roll the dough out as thinly as possible and cut 24 circles, each slightly larger than 10 cm/4" in diameter. Place a spoonful of the filling in the middle of half the pasta circles and moisten the edges with a little water. Top with the remaining pasta circles and seal tightly by pressing with your fingers.
Use a 10 cm/4" cutter to trim the edges off each of the ravioli. Bring a large pan of salted water to a boil and simmer the ravioli for about 5 minutes. Remove from the pan with a slotted spoon and keep warm.
Lay the chives onto serving dishes and top with the ravioli. Quickly reheat the sauce, stir in the lemon zest and chopped chives and season with salt and pepper. Drizzle the sauce over the ravioli and serve immediately.