Preheat oven to 350°F (175°C).
Pat chicken dry, season with salt and pepper.
In a bowl, whisk sofrito with honey Dijon mustard. Coat chicken thoroughly.
Heat oil in a cast iron skillet over medium-high. Sear chicken 3 minutes per side until golden.
Toss Brussels sprouts in remaining marinade, season with salt and pepper.
Nestle Brussels sprouts around chicken in the skillet.
Bake uncovered for 40 minutes, until chicken is cooked through and sprouts are caramelized.
Serve hot, spooning pan juices over the top.