Combine all the ingredients for the dressing in a small mason jar. Close with the lid and shake well. Set aside.
FOR THE SALAD
First, add Brussels sprouts in a food processor with the slicing attachment and pulse until the Brussels sprouts are thinly sliced. If you don’t have a food processor, you can use a mandolin (I love this one.) or a very sharp knife.
Heat a skillet over medium high heat. Add bacon and cook until brown and crispy, about 5-7 minutes. Transfer to a paper towel-lined plate.
Place the shredded Brussels sprouts, kale and onion in a large bowl. Drizzle the salad with the dressing and toss well.
Season with salt and pepper.
Top with bacon before serving.
If you don't like to eat raw kale or Brussels sprouts you can sauté them for 3-5 minutes in the same skillet you use to cook the bacon. Use some of the bacon fat (about 1 tablespoon) to sauté them.