Preheat the oven to 350F.

Make the rice by roughly chopping the broccoli (both florets and stalk) and adding it to a blender. Add cold water to cover about three-quarters of the broccoli. 

Pulse a few times until rice has formed, then drain it through a fine mesh sieve.

Transfer it to a bowl, and add the sour cream, shredded cheese, and black pepper. Mix to combine, then spoon it into a small baking dish. 

Cover with foil and bake for 20 minutes, then uncover and bake for another 10 minutes.