Whisk together soy sauce, broth, and brown sugar substitute in a small bowl. Set aside.
Heat 1 tablespoon of oil in a large skillet over medium-high heat. Season chicken with pepper and add to pan in a single layer, cooking in batches if needed. Cook for 4-5 minutes or until browned and cooked through. Set aside on a plate and cover to keep warm.
Reduce heat to medium and add remaining oil and green beans to skillet. Cook for 4-5 minutes until tender-crisp. Add garlic and ginger and cook for 30 seconds more.
Add chicken and sauce mixture to skillet, cooking for 3-4 minutes or until heated through.
To thicken the sauce, whisk together 4 tablespoons water with xanthan gum until smooth. Move chicken and green beans to the side of the pan and whisk xantham gum into the sauce. Stir to coat everything with sauce.
Notes
Freeze raw chicken breasts for about 20 minutes to make slicing easier.
Cook chicken to a temperature of 165°F for safe consumption.
Substitute a tablespoons of heavy cream for Xanthan gum to thicken the sauce.
Refrigerate leftovers for up to three days, or freeze for up to four months.