1. In a bowl, mix the apples, sugar, salt, and cinnamon. 2. In a saute pan, melt the butter and add add the apple mixture. Cook until the apples are slightly softened. Add the walnuts, until they are warm. Remove from heat. 3. Roll out the puff pastry and lay on top of a greased cookie sheet. Place the Brie wedge in the center of the pastry. Pour the apple and walnut mixture on top. 4. Fold the puff pastry around the Brie and brush with an egg wash. 5. Place in oven for about 20 minutes, or until the pastry is golden brown. 6. Let rest for at least 5 minutes before cutting open.