Chill the whipping cream and sour cream. In a mixing bowl, whip the cream until soft peaks form. Lightly whisk the sour cream by hand until smooth.

Once the cream is whipped, gradually fold in the sour cream to make a thick mixture. Dissolve the gelatin in warm water, then mix a small amount of the cream mixture into the gelatin to combine. Add this back into the main cream mixture and blend well. Transfer the cream to a piping bag. Using a round springform pan without the bottom, mix the instant coffee and rum together. Dip the ladyfingers briefly into the coffee mixture and arrange them in the bottom of the pan, then add a layer of cream.

Add a layer of thinly sliced fruit, and arrange fruit slices around the inside edge of the pan with the cut sides facing out for a decorative look when unmolded. Continue layering ladyfingers, cream, and fruit until all ingredients are used. Spread a final layer of cream on top, pipe cream in shell shapes, and decorate with assorted fruit.

Refrigerate for about 4 hours until set, then carefully remove the pan. This beautiful cake can also be used as a birthday cake and is light and easy to enjoy.