Preheat the oven to 400°F.

Heat a 10-inch cast iron skillet over medium heat. Add bacon, and cook until crispy, about 10 minutes, flipping as needed so the bacon does not burn. Remove bacon from the skillet, and drain on paper towels. Remove the skillet from the heat, and measure out 2 tablespoons of bacon grease from the pan to use for the vinaigrette.

Sprinkle chicken thighs with a bit of salt and pepper. Return the cast iron skillet to the heat, and add chicken thighs. Cook until lightly browned on each side, about 10 minutes, flipping halfway through. Remove from the heat and set aside.

While the chicken is cooking, make the vinaigrette. Add all vinaigrette ingredients to a glass Mason jar. Place the lid on the jar, and shake well. Set aside. NOTE: if you do not have a glass jar, simply whisk together the ingredients in a medium bowl, and set aside.

Next, add the Brussels sprouts to the skillet, and cook, stirring occasionally, until they begin to brown, about 5 minutes. Add the butternut squash, and stir together. Let the veggies cook until they begin to become tender and lightly browned, about 5-8 more minutes. Add about half the vinaigrette mixture, and stir together until the veggies are well coated. Return the chicken thighs to the skillet, and drizzle with the remaining vinaigrette.

Place the cast iron skillet in the oven, and bake for about 15 minutes, or until the chicken is cooked through and the veggies are tender. Remove from the oven and serve.