In a small mixing bowl, combine the low sodium soy sauce, water, sesame oil, arrowroot starch, coconut sugar, garlic, and fresh ginger. Mix vigorously until no clumps remain. Set sauce aside until ready to use.
Heat large skillet over high heat and add the olive oil.
Add the steak and cook for 4-6 minutes, or until it starts to cook through. Add the broccoli, onion, and sauce into the skillet toss everything to coat. Cook for 4-5 more minutes, or until the broccoli starts to turn bright green, the steak is cooked through, and the sauce has thickened.