Step1
Preheat oven to 375 F. Bring a large pot of salted water to a boil over high heat; add the broccoli florets, and cook for three minutes (the broccoli should turn a very bright green). Strain and place on a sheet pan in one layer until fully cooled.
Step 2
In a large bowl, combine the mayonnaise, cream cheese, mozzarella, both cheddars, hot sauce, granulated garlic, onion powder, salt, and pepper.
Step3
Add the sour cream and about a third of the broccoli to a blender; blend until mostly smooth, and add to the large bowl, stirring until incorporated. Add the remaining broccoli, and mix until evenly distributed. Transfer to an oven-safe baking dish, and bake for 20-25 minutes, until just starting to turn golden brown on top. Allow to cool 5-10 minutes before serving.