How do you plot your stories so quickly?

I have to outline before I write! Honestly I usually have plot bunnies, like hundreds, running around. When I find a character (original or one for a fanfic) for whom I’d like to throw this plot bunny at them, things usually start to take shape. But outlining is actually the hardest part for me. But if I don’t have a detailed outline for what I want out of each chapter in the fic (that’s why I always know how many chapters it will be, approximately) i will fall flat on my face and not be able to write it lol.