Bring a pot of water with a steamer basket on top to a boil. Add the Brussels sprouts and cover. Let them steam for about 5 to 10 minutes, until slightly tender.
Meanwhile, add bacon and onion to a large cast iron skillet over medium-high heat. Cook the bacon until the fat is rendered and it is starting to crisp.
Remove the Brussels sprouts from the steamer basket and add into the pan with the bacon and onion. Let the Brussels sprouts brown and caramelize in the bacon drippings for about 3 to 4 minutes.
Season with salt and pepper to taste and then serve immediately. Enjoy!
Notes
The Brussels Sprouts should be crisp-tender when finished. If you prefer them softer, you can steam them for a few minutes longer prior to adding to the bacon grease.