In a marinating bowl, combine the soy sauce, water, garlic, black pepper, red pepper flakes*, Worcestershire sauce, freshly squeezed lemon juice, and grated lemon rinds.
Add the thinly sliced venison cutlets. Gently stir every thing together to coat with the marinade. Cover the bowl then store in the fridge for 3-4 hours or overnight.
Slice the onions and mushrooms. Set aside until it's time to cook.
Once ready to cook, heat up oil in a wok or saute pan. Slowly add the marinated venison cutlets and the marinade into the saute pan. Brown for 8-10 minutes. Stir in 1 1/2 cup of water. Cover and cook until meat are soft and tender. Stir occasionally. (Add more water if needed and cook a little bit longer to tenderize the meat and reduce the sauce.)
Sprinkle red pepper flakes. This is optional.
Stir in the sliced onions. Cook for 2 minutes or so.
Stir in the sliced mushrooms. Cook for another 2 minutes.
VOILA!
