Slice beef very thin, approximately 1/4 to 3/8 inches thick. If you are using skirt steak cut the meat diagonally, it will help make the meat more tender.

Place meat between sheets of plastic wrap. Use a meat tenderizer and gently pound meat into uniform pieces.

Place corn starch in a bowl.

Dip steak pieces into corn starch. Shake off excess.

Place pieces on a plate and allow meat to rest for 5 - 10 minutes, so the coating sticks to the meat.

In a wok or large skillet, heat vegetable oil and sesame oil over high heat.

When oil is hot and shimmering, carefully add a few strips of beef and sauté until just done, and the outside begins to crisp. Remove meat from pan. Repeat until all meat is cooked. Leave oil in pan

Leave oil in wok or skillet and add minced ginger and garlic. Sauté for about 60 seconds.

Add soy sauce, water, Maggi seasoning, brown sugar, and rice wine vinegar. Stir until the sauce thickens.

Return meat to pan. Add quartered button mushrooms and 1/2 of the chopped scallions. Cook for another 60 seconds or so, to heat through.

Serve hot over steamed rice or Chinese noodles. Scatter remaining scallions over the beef, to garnish.