Place a cast iron skillet on the stove top leaving the heat off. Spray it with non-stick spray.
Place the chicken thighs, skin side down, in the skillet.
Arrange the potatoes around the chicken and sprinkle with course sea salt and black pepper. Turn the heat on to medium.
Cook, stirring the potatoes occasionally, until chicken skin is browned and crisp, about 15 minutes.
Turn off the burner heat and flip the chicken thighs over. Place the skillet in the oven. Bake 15 – 20 minutes until the thighs internal temperature reaches 165 degrees F.
Transfer the chicken and potatoes to a plate, keeping as much of the drippings in the skillet as possible.
Over low heat, add to the skillet, the garlic, mustard, and vinegar.
Add the spinach leaves and stir to coat. Cook and stir just until wilted, about 3 minutes.
Serve with the chicken and potatoes.
Video
Notes
1 serving includes 1 chicken thigh, half of the red potatoes, and half of the spinach