Slice mushrooms. Set aside.
Slice green onions, separate green and white parts. Set aside.
Place tenderized beef strips in a colander and rinse beef thoroughly to remove all the baking soda. The baking soda will leave a bitter taste, so be sure to wash beef well to remove it completely.
Pat beef strips dry with a paper towel.
Heat oil in a wok or large skillet over medium high heat.
Add the sliced mushrooms and cook them until they release their liquid. Continue to cook until mushrooms begin to brown along the edges.
Add the white part of the green onions and the minced garlic to the pan and cook, stirring continuously for another minute, until green onions start to soften.
Add the beef strips to the wok. Cook for another 1-2 minutes until beef is cooked through.
Stir the sauce and add it to the pan. Cook until the sauce thickens, 1-2 more minutes, stirring constantly.
Remove from heat.
Serve immediately over a bed of steamed rice and garnish with reserved green onions.