As Nicholas said, you are introducing air to the heavy cream, thus making it foamy. Adding sugar would add some stability, but if it fell apart that might be a sign that you overwhipped it.
Most likely, your bakery is not using...
My name is Charbel. I am currently a pastry and baking student with one more class left.
I choose this career path about ten years too late (cliché: it's never too late!).
I have a bachelor in chemistry and an MBA. Neither...
1. Letter fold
2. 3 times
3. Make sure you let the dough rest about 20 minutes between folds, in the fridge
4. Butter is always going to leak a bit. Too much leaking might indicatenthat you are using too much butter.
5. I bake it at 400F...