Preheat oven to 350°F. Spray a 9x13-inch baking dish with baker’s spray. Set aside.

In a large bowl, whisk the French vanilla cake mix, water, vegetable oil, and eggs together for 2 minutes. Follow package directions for a 9x13 sheet cake.

Pour the cake batter into the prepared dish and bake for 27-30 minutes or until a toothpick comes out clean.

Cool the cake for 20 minutes, then poke holes over the entire surface using the handle of a wooden spoon.

Microwave the blackberry preserves on high for 45 seconds to 1 minute, then stir until pourable.

Pour the warmed preserves evenly over the cake, concentrating on the holes. Use an offset spatula to spread evenly.

Whisk the instant white chocolate pudding mix and whole milk in a large bowl for 3 minutes until thickened.

Fold in the whipped topping until fully combined.

Spread pudding mixture over the cake, avoiding the blackberry preserves.

Sprinkle white chocolate chips over the pudding layer.

Garnish each serving with a fresh blackberry in the center for presentation.

Refrigerate for at least 6 hours or overnight before serving.