Preheat your oven to 350°F (175°C).
Core the apples, making sure to leave the bottom intact to hold the filling.
In a mixing bowl, combine the softened cream cheese, granulated sugar, vanilla extract, ground cinnamon, and salt. Mix until smooth and creamy.
Gently fold in the crushed graham crackers and chopped walnuts (if using) into the cream cheese mixture.
Stuff each apple with the cheesecake filling, packing it in gently.
Place the stuffed apples in a baking dish and drizzle the melted butter over the tops.
Bake in the preheated oven for 25-30 minutes, or until the apples are tender and the filling is slightly golden.
Remove from the oven and let cool for a few minutes before serving. Top with whipped cream if desired.