Cut the florets off the head of broccoli to roughly the same size. Peel the stalk of broccoli if you want, and slice it into 1/4-1/2 inch thick coins. Put a few tablespoons of olive oil into a heavy pan (like a cast iron frying pan), and put it on high heat until the oil is quite hot and almost smoking. Dump the broccoli into the pan all at once and cover it quickly with a lid. Cook for 2 minutes, don't lift the lid (no peeking). Take the lid off, season the broccoli with salt and pepper, shake the pan to move the broccoli around, add about a tablespoon of butter, re-cover and cook for 2 more minutes on high. Check the broccoli to see if it's done (it should be cooked - partially scorched, partially green). If it isn't ready, cover the pan and cook for about 2 more minutes.