Prepare sponge cake: line the bottom of a 9-inch spring form pan with parchment paper. Preheat oven to 350F. Place eggs and sugar into mixer bowl and whisk on high speed until eggs are thick, foamy and almost white in color. Sift together flour and baking powder. Using spatula, carefully sift flour into eggs and fold gently after each addition. Pour batter into prepared pan, spread evenly to sides and bake in preheated oven until golden brown on top. Remove cake from oven and let cool completely before slicing in half. 

For fruit mousse: wash and dice fruit and set aside. Line 9-inch spring form pan with parchment paper on bottom and sides, leaving 2 inches overhang for the sides.

Combine Jello/fruit gelatin and 1 cup boiling water; stir until completely dissolved. Add cold water and stir. Place gelatin into refrigerator to set. Important: the gelatin needs to set only about half way! Stir the Jello often so it doesn’t set completely and firmly. Remove from the refrigerator promptly. If gelatin sets too firmly, remove and let stand at room temperature to soft up.

Place heavy cream and sugar into mixer bowl. Whisk on high speed until light and fluffy. Gradually add the softened cream cheese and whisk until no clumps remain. Whisk in Jello. Fold fruit in by hand.

To assemble cake: place 1 layer of the sponge cake on the bottom of the prepared spring form pan. Top with half of the mousse, followed by second half of the sponge cake. Spoon remaining mousse on top. Spread evenly with spatula. Place into refrigerator for several hours or overnight to set completely.

Garnish top of cake with fresh fruit or whipped cream if desired. To remove cake from pan, undo spring form and carefully peel back parchment paper.