In a medium saucepan over medium heat, whisk together 2 tablespoons of cornstarch and ¼ cup of sugar. Add 1 cup of fresh raspberries and 2 tablespoons of lemon juice, stirring continuously until the mixture thickens and bubbles, about 5-7 minutes. Once thickened, remove from heat and let it cool completely before adding it to your cheesecake.

In a mixing bowl, combine 1 ½ cups of graham cracker crumbs, ½ cup of melted unsalted butter, and ¼ cup of sugar. Mix until well combined, resembling wet sand. Press this mixture firmly into the bottom of a 9x13 inch baking dish, ensuring it’s evenly spread. Chill the crust in the refrigerator while you prepare the filling, about 10 minutes.

In a large bowl, beat 16 ounces of room-temperature full-fat cream cheese with 1 cup of powdered sugar using an electric mixer until smooth and creamy, about 3-5 minutes. Gradually add ½ cup of milk and 1 teaspoon of vanilla extract, mixing until combined. Gently fold in 8 ounces of thawed Cool Whip until there are no more streaks, creating a light and fluffy cheesecake filling.

Spread the cream cheese mixture evenly over the chilled graham cracker crust, smoothing the top with a spatula. Carefully layer the cooled raspberry filling on top of the cheesecake, drizzling it lightly and leaving some swirls visible for a marbled effect.

Cover the assembled cheesecake with plastic wrap and refrigerate for at least 6 hours, or overnight if possible, to allow the layers to set properly. Once set, it will be ready to serve and enjoy.