Freeze tofu. Thaw tofu and drain as much water as possible. Cut tofu into 1/4-1/2 in cubes.
Chop onion into medium size wedge pieces. Chop water chestnuts (or use sliced in the can)
Mix vegetable stock, soy sauce, sherry, ground red pepper and garlic/red chili sauce (I use Sun Luck brand) in a mixing bowl.
Stir fry tofu in canola oil until golden brown. Remove tofu onto paper towels to blot. Remove excess oil from wok. Stir fry onion, water chestnuts and frozen stir fry mix (your favorite blend). Add tofu to veggies after 1-2 minutes. stir fry another 1-2 minutes. Add sauce and cook to boil. Cover and simmer until sauce has thickened. Serve over rice.