• Line the sides of a 8 or 9-inch springform pan with parchment paper. Set aside.
• Add gelatin powder and water to a small bowl and stir. Let it sit to firm up while you move on to the next step.
• Add strawberries to a medium sized saucepan. Cook over medium heat until the strawberry juices start to boil. Simmer for a few extra minutes until berries are soft, then remove from heat.
• Remove 1 cup of strawberries and their juices from the saucepan, and set aside. Add the remaining strawberries from the saucepan into a blender.
• Microwave the gelatin mixture for about 15 seconds, or until melted. Add this to the blender with the strawberries. Blend until the strawberries have pureed. Set aside to cool while you make the whipping cream.
• In a large bowl, add heavy whipping cream, powdered sugar, and vanilla. Beat on high until it becomes stiff peaks. Remove 1 cup whipping cream to a small bowl to use later.
• Add blender strawberries to the large bowl, and fold them together with a spatula until combined.

Assemble

• Cut a straight edge to the end of the ladyfingers that go vertically up the sides of the springform pan. Place enough ladyfingers around the sides of the pan so that there are no spaces.
• Arrange a layer of ladyfingers at the bottom of the pan. You may need to cut some so they fill in the gaps.
• Add half of the reserved cooked strawberries on top of the bottom layer of ladyfingers.
• Add half of the strawberry whipped cream on top, then follow with another layer of ladyfingers, the rest of the cooked strawberries, and the rest of the strawberry whipped cream. Smooth the top with an offset spatula.
• Use the reserved whipped cream to decorate the top of the cake. I used a star piping tip. Arrange strawberries on top as decoration.
• Chill the cake in the refrigerator for at least 6 hours or overnight for the mousse to firm up. Release the cake and tie a ribbon around it for decoration before serving.
• Store leftovers in the refrigerator for up to 3 days.