Roughly diced the chicken and ham and place in a food processor. Process until finely chopped and set aside.
Place the milk and bread in a frypan over low heat. Stir until the mixture turns into a paste. Set aside.
Melt butter in a large frying pan. Add onion shallots, mushrooms and lemon juice. Cook, stirring, until mushrooms have sweated and liquid has evaporated. Let cool slightly.
In a large mixing bowl, combine chicken and ham mixture, bread mixture and mushroom mixture. Add egg yolks, creme fraiche, sherry, almond meal, paprika, cayenne, thyme, salt and pepper. Mix with your hands until well combined.
Beat the egg whites until stiff. Gently fold into the sausage mixture. Fold in the parsley and optional truffle shavings. Cover and chill in the fridge 1 hour.
Soak the hog casing in cold water for 30 minutes and run water through it to remove excess salt.
Using a medium sausage stuffing attachement, place the casing over the end of the tube. Start passing the mixture through the funnel, stopping when it comes out the other end. Tie the casing in a knot over the end, then continue passing the meat mixture through the funnel, supporting the sausage with your other hand. Once meat mixture is used up, tie the other end of the casing in a knot.
Twist the sausage at regular intervals to form links of desired length, alternating the direction of twisting.
Add the sausages to a large saucepan of lukewarm water with the chilli and the bay leaf. Over low heat, bring the water to just below simmering, about 90 degrees C. Keep it there for 40 minutes. Drain and run the sausages under cold water to stop cooking process.
To serve, fry the sausages in butter over medium heat, about 7 minutes per side.