Preheat your oven to 325°F (165°C).

In a bowl, mix together the crushed graham crackers, sugar, and melted butter until combined. Press this mixture firmly into the bottom of a greased 9x9-inch baking pan. Bake for about 10 minutes or until the crust is golden brown. Let it cool.

In a mixing bowl, beat the softened cream cheese with sugar until smooth. Add in the vanilla extract and eggs, mixing until just combined. Gently fold in the crushed pineapple. Pour this cheesecake filling over the cooled crust and spread it evenly. Bake for 25-30 minutes, or until the center is set but still slightly jiggly. Allow cooling completely.

While the cheesecake layer cools, beat the heavy whipping cream with powdered sugar and vanilla extract until stiff peaks form. Gently fold in the reserved pineapple juice.

Once the cheesecake layer has cooled, spread the pineapple mousse evenly over the top. Chill the whole pan in the refrigerator for at least 2 hours, or until set.

Cut the bars into squares before serving. Top with fresh pineapple chunks if desired.