Place the beef strips in between two paper towels and place in the freezer while you prepare the sauce. This will dry out the meat, making it even crispier when cooked.
In a mixing bowl, whisk together the soy sauce, rice vinegar, water, Erythritol and chili flakes.
Heat half the amount of butter in a non-stick skillet and sauté the beef, for 5-7 minutes on each side, until golden brown working in batches if needed, making sure the strips are not touching each other.
Remove the beef from the pan and heat the remaining butter.
Sauté half the amount of green onions, reserving the rest to garnish, the orange zest and grated ginger for 5 minutes.
Add the garlic and xanthan gum and stir.
Add the rice vinegar and the soy sauce mixture and simmer until it reaches a glossy, thick consistency.
Add the beef strips and stir to coat.
Serve hot garnished with green onions and optionally orange slices.