1. Preheat your oven to 350°F (175°C) and grease a 9×13-inch baking dish.
2. In a large bowl, combine the vanilla cake mix, water, vegetable oil, and eggs. Beat on medium speed for 2 minutes until smooth and well-blended.
3. Pour the batter into the prepared baking dish and bake for 28-32 minutes, or until a toothpick inserted into the center comes out clean.
4. While the cake is baking, prepare the berry mixture. In a medium saucepan over medium heat, combine the strawberries, blueberries, raspberries, and a splash of water. Cook until the berries are soft and release their juices, about 5 minutes.
5. Stir in the strawberry gelatin until dissolved, then remove from heat.
6. Once the cake is baked, allow it to cool slightly. Using the handle of a wooden spoon, poke holes evenly across the entire cake.
7. Pour the sweetened condensed milk over the cake, letting it seep into the holes.
8. Follow with the berry and gelatin mixture, ensuring it fills the holes and covers the top of the cake.
9. Refrigerate the cake for at least 2 hours, allowing the flavors to meld.
10. Before serving, whip the heavy cream with powdered sugar and vanilla extract until stiff peaks form. Spread the whipped cream over the chilled cake.
11. Garnish with additional fresh berries if desired.

Remember, cooking is about intuition and joy. Trust your senses as you go through each step, a lesson Nonna Rosa instilled in me during our long afternoons in the kitchen.