Heat wok over medium-high heat, add 2 ounces of oil and stir-fry meat until brown, mashing with a fork to break into small pieces. Drain off fat and set meat aside. Wash pan and dry thoroughly.
Heat 1 ounce of oil over high heat for 1 minute. Add onions and saute for 2 to 3 minutes or until limp.
Add cabbage and continue to cook, stirring frequently, for another 2 to 3 minutes or until cabbage is crisp-tender.
Add bean sprouts, scallions, and tofu, mix well and cook for 1 to 2 minutes more.
Remove pan from heat and pour cooked mixture into a colander to drain excess liquid.
In a large bowl, combine meat, vegetables, hoisin, salt, and pepper and mix well.
Place 1 wonton skin on a flat surface. Cover remaining skins with a slightly damp kitchen towel (not terry cloth) so they won't dry out. Brush the edges of skin with a beaten egg. Place about 1 teaspoon of filling mixture just above the center of skin. Fold skin in half over filling to form a triangle and press edges together to seal. Repeat with remaining skins.
Fill and preheat fryer to 375 degrees F. and deep-fry dumplings until golden brown. Serve immediately with vinegar-soy dipping sauce.
For vinegar-soy sauce: Combine all ingredients in a bowl. Stir to dissolve sugar.