Preheat the oven to 350°F (175°C). Grease and flour a 9x13 inch baking pan.
In a large mixing bowl, combine the cake mix, water, vegetable oil, and eggs. Mix until well combined and smooth.
Pour the batter into the prepared baking pan and bake for 30 minutes or until a toothpick inserted into the center comes out clean. Allow the cake to cool in the pan for 10 minutes.
While the cake is cooling, prepare the raspberry sauce. In a saucepan over medium heat, combine the raspberries and granulated sugar. Cook until the raspberries break down and form a sauce, about 5-7 minutes. Remove from heat and let cool slightly.
Once the cake has cooled for 10 minutes, use a toothpick or skewer to poke holes all over the cake, about 1 inch apart.
Pour the raspberry sauce evenly over the top of the cake, making sure it seeps into the holes.
In a separate bowl, heat the white chocolate chips in the microwave until melted, about 30 seconds, stirring until smooth. Let it cool slightly.
In a large mixing bowl, whip the heavy cream until soft peaks form. Add the vanilla extract and powdered sugar, and continue to whip until stiff peaks form. Gently fold in the melted white chocolate until well combined.
Spread the white chocolate whipped cream over the top of the cake, covering the raspberry sauce.
Garnish with fresh raspberries and white chocolate shavings if desired.
Cover the cake with plastic wrap and refrigerate for at least 2 hours before serving to allow the flavors to meld.