Place the chicken breast in a shallow bowl and pour buttermilk over it, letting it marinate for at least 15 minutes.
In a separate small bowl, whisk together the arrowroot powder, garlic powder, onion powder, sea salt, and black pepper.
Remove chicken from the buttermilk, letting excess drip off, then dredge thoroughly in the seasoned arrowroot mixture.
Heat avocado oil in a skillet over medium-high heat until shimmering.
Carefully place the chicken in the skillet and cook for 5-6 minutes per side until the coating is golden brown and the internal temperature reaches 165°F.
While the chicken cooks, whisk together the Dijon mustard and honey in a small ramekin.
Steam the broccoli florets until tender-crisp.
Serve the crispy chicken alongside the steamed broccoli with the honey mustard sauce on the side.