Preheat oven to 350°F.
Crush graham crackers into fine crumbs. Combine with butter and granulated sugar, mixing until evenly moistened.
Press mixture firmly into the bottom of a parchment-lined 9x13-inch baking dish. Bake for 8-10 minutes, then let cool completely.
In a large mixing bowl, beat cream cheese until smooth. Add sweetened condensed milk, granulated sugar, orange juice, orange zest, and orange extract if using. Beat until fully combined and creamy.
In a separate bowl, whip heavy cream with powdered sugar until stiff peaks form.
Gently fold whipped cream into the orange-cream cheese mixture until fully incorporated.
Spread filling evenly over cooled crust. Smooth the top with a spatula.
Cover and refrigerate for at least 4 hours, or until set.
Just before serving, spread Crème Chantilly over the top and cut into bars.