Prepare the Oven and Pan: Preheat the oven to 325°F (163°C). If using a springform pan, lightly grease the sides. Place the Keebler graham cracker crust on a baking sheet for extra support during baking.
Mix the Filling: In a large mixing bowl, beat the softened cream cheese with an electric mixer on medium speed until smooth. Add sugar and beat until fully incorporated. Add eggs one at a time, mixing each thoroughly before adding the next. Add vanilla extract and mix again.
Add Cream and Sour Cream: If using, add the sour cream and heavy cream to the mixture and beat until everything is well combined and smooth.
Fill the Crust: Pour the cheesecake filling into the prepared Keebler graham cracker crust, spreading it evenly.
Bake: Place the cheesecake in the preheated oven and bake for 40-45 minutes, or until the center is set but still slightly jiggly. Avoid over baking to prevent cracks.
Cool and Rest: Allow the cheesecake to cool in the oven with the door slightly ajar for 1 hour. After that, transfer to a cooling rack and let it cool completely at room temperature. Once cooled, cover and refrigerate for at least 4 hours (overnight for best results).
Serve: Once chilled, carefully remove the cheesecake from the spring form pan and slice it. Optionally, top with fresh berries, chocolate drizzle, or whipped cream before serving.
