In A Large Bowl, Blend Cornstarch, Garlic, 1 Teaspoon Ginger, And 2 Tablespoons Vegetable Oil Until Cornstarch Is Dissolved. Mix In Broccoli, Snow Peas, Carrots, And Green Beans, Tossing To Lightly Coat. Heat Remaining 2 Tablespoons Oil In A Large Skillet Or Wok Over Medium Heat. Cook Vegetables In Oil For 2 Minutes, Stirring Constantly To Prevent Burning. Stir In Soy Sauce And Water. Mix In Onion, Salt, And Remaining 1 Teaspoon Ginger. Cook Until Vegetables Are Tender But Still Crisp.