Triple Berry Cake

So I saw THIS post the other day and knew that I would immediately be making such a cake. Only I upped the ante with the box cake and it turned out pretty delicious if I do say so myself. I added 1 c sour cream, 1 tsp vanilla and 1 1/2 tsp almond extract to the other ingredients listed on the back of the box. The only problem - I have NO freaking clue how she made the whip cream so smooth and perfect. I even added extra powdered sugar in attempts to make it stiffer and more frosting-like. But to no avail. And what's worse - the moment I cut into that sucker it collapsed onto the counter. AND we had guests....talk about embarrassing. But I salvaged a few pieces of goulash looking cake for everyone and we enjoyed the heap of berries and cream.