Preheat the oven to 400 degrees.

Wash and trim ends of Brussels sprouts. Slice each Brussels sprout in half and remove the outer leaves.

Place bacon in a cast iron skillet over medium high heat. Flip occasionally until cooked through. Remove bacon and set aside. Drain off and reserve excess bacon grease, but leave some in the pan for the first round of Brussels sprouts.

Spread one layer of Brussels sprouts evenly in the cast iron pan. You may need to cook the Brussels sprouts in several batches because you want each one to be touching the bottom of the pan to receive a good sear. Add back in bacon grease as necessary for your cooking fat.

Once the Brussels sprouts are in the pan resist the urge to touch them! Just let them sear for a few minutes (probably 3 or 4 minutes depending on the heat in your pan). Then remove them from the cast iron pan and place them on a sheet pan with parchment paper or a Silpat mat while you sear the next batch.

Once all Brussels sprouts have been seared, put sheet pan in the oven for 10-15 minutes to finish cooking. Sprinkle with salt and pepper and shake the pan half way through the cooking time.

While the Brussels sprouts are in the oven, crumble all the strips of bacon. You will use one for the aioli and the rest will be added in directly with the Brussels sprouts.

Combine all aioli ingredients in a small bowl and place in the refrigerator until ready to serve.

When Brussels sprouts are roasted to perfection, remove from oven and transfer to serving dish. Add crumbled bacon and serve with bacon garlic aioli on the side!