In a medium saucepan over medium heat, combine cornstarch and sugar. Add fresh raspberries, a splash of water, and a squeeze of lemon juice. Cook while gently stirring for about 5–7 minutes until the mixture thickens and becomes syrupy. Once thickened, remove it from the heat and let it cool completely while you move on to the next steps.

In a mixing bowl, combine melted butter with graham cracker crumbs and sugar, blending until the mixture resembles wet sand. Press this crumb mixture firmly and evenly into the bottom of a 9x13 inch baking dish. Bake in a preheated oven at 350°F (175°C) for 8–10 minutes, then cool.

In a large mixing bowl, use an electric mixer to beat together softened cream cheese, powdered sugar, milk, and vanilla extract until smooth and creamy, around 3–4 minutes. Once smooth, gently fold in the fully thawed Cool Whip until just combined.

Spread the cream cheese filling evenly over the cooled crust, smoothing it into the corners. Take your cooled raspberry topping and layer it artfully on top of the cheesecake filling.

Cover the assembled cheesecake with plastic wrap and refrigerate for at least 6 hours, or overnight if you can wait. Once fully chilled, your Creamy Raspberry Cheesecake is ready to serve.