Season the 1 kg pork neck with salt and pepper. Heat oil in a large pot or Dutch oven over medium-high heat and brown the meat on all sides. Add a small amount of broth, reduce heat to medium-low, cover, and simmer for about 1 hour until the pork reaches 63°C (145°F) internal temperature. Add more broth as needed if the liquid reduces significantly. Remove from heat and let cool completely, then cut into thin slices.
In a saucepan, combine the Camembert, cream cheese, and the remaining broth. Heat over medium-high heat, stirring frequently, until the mixture comes to a boil, about 5 minutes. Remove from heat and stir in the 2 cups of sweet cream. Return to a boil over medium-high heat for about 1 minute, then remove from heat. Season with salt and pepper to taste. In a baking dish, layer the sliced pork with the drained mushrooms from the 1 large can. Pour the cheese sauce over the meat and mushrooms. Cover and refrigerate overnight (at least 8 hours).
Preheat the oven to 200°C (392°F). Bake the casserole for about 30 minutes until heated through.