Preheat the oven to 160C/325F/Gas 3.
Bring a large pan of stock to the boil, add the pork bones and allow to bubble for 45 minutes on a very low heat.
Using a mortar and pestle, crush the salt, pepper and juniper berries together. Mix them with the flour in a large mixing bowl.
Heat the olive oil in a large casserole and brown the pork in batches, transferring the meat each time to the bowl with the seasoned flour. Mix the meat well.
Fry the onions in the same casserole until softened and translucent. Shake off any excess flour from the pork and return to the casserole. Fry for three minutes to cook the flour through.
Ladle the stock (without the bones) over the casserole and stir well, ensuring that there are no lumps of flour.
Take the sliced discs of apple and turnip and layer them over the casserole alternating between the two. Scatter little knobs of the butter over the top. Place the lid over the casserole or cover with foil. Bake for two hours, removing the lid or foil, for the last 30 minutes.
Serve in deep bowls with crusty bread.